The two bombs detonated in Boston near the finish line of the marathon sent a wave of panic across the country as fears of a copycat attack gripped cities from Washington, D.C. to New York.
'We're stepping up security at hotels and other prominent locations in the city through deployment of the NYPD's critical response vehicles (CRVs) until more about the explosion is learned,' NYPD spokesman Paul Browne said.
Security was increased at the White House and Pennsylvania Avenue has been shut down.
London Marathon officials are reviewing security plans for its race this Sunday.
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On the lookout: Police officers on duty at Grand Central Terminal in Manhattan yesterday after New York City heightened its security
Inspection: A US Army soldier inspects a corner in Grand Central Terminal in Manhattan
Close watch: Police officers and a US Army soldier keep a close watch over the busy terminal
A S.W.A.T officer checks planters on a median in a road next to Tufts Medical Center in Boston
'This changes everything [in New York],' one source told the New York Post.
'Everyone’s on high alert. Our marathon was canceled in November. Who knows if that changed someone’s plans?'
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Should Sunday's London Marathon still go ahead after the Boston blasts?
Yes
No
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The New York Metropolitan Transportation Authority said the MTA police would increase patrols and bag inspections on the Metro-North and Long Island Rail Road.
The NYPD will give 'additional attention' to the subways as well.
Mayor Michael Bloomberg said security is being upped both visibly and in covert ways, NBC reported.
'We have 1,000 members of the NYPD assigned to counter-terrorism duties, and they - along with the entire NYPD and the investments we have made in counter-terrorism infrastructure - are being fully mobilized to protect our city,' he said in a statement.
A garbage can on a subway platform was seen taped up so that nothing could be tossed inside - preventing a bomb from being placed and left behind.
Standing guard: A Los Angeles Sheriffs Counter Terrorism Unit deputy patrols Union Station before the start of Los Angeles Dodgers game in Los Angeles on Monday
Stop and search: Amtrak Explosive Detection K-9 officer Kenneth Wolf and his dog Teddy ask a passenger to inspect his luggage before boarding a departing train at Union Station in Los Angeles
Bomb squad: Sgt Darryl Judge with the Richland Police bomb squad positions a device next to a briefcase found Monday in Richland, Washington after police received a call of a suspicious package around 2pm
NYPD said it was increasing patrols and security at hotels and other prominent locations until it knows more about the terror attack in Boston
Dozens of uniformed NYPD officers set up in the center of New York City's Times Square following news of the Boston Marathon explosions
A Twitter user posted this picture from a New York City subway platform that shows a garbage can taped up, preventing an explosive device from being tossed inside and left
New York on high alert following Boston blasts
In Washington, the White House increased security outside the building with Secret Service establishing a broader 'perimeter.'
Secret Service spokesman Ed Donovan says the measure was taken 'out of an abundance of caution'. He says it is not unusual to expand or contract the security perimeters.
Shortly after the explosions Monday, Secret Service shut down Pennsylvania Avenue outside the White House, cordoning off the area with yellow police tape.
Several Secret Service patrol cars also blocked off the entry points to the road.
U.S. Secret Service agents stand on top of the White House amid the heightened security around the area (left) along with more squads at Madison Square Garden in New York
A Secret Service officer stands guard in front of the White House after the surrounding area was closed
A couple stands behind a police line on Pennsylvania Avenue in front of the White House
The White House was not on lockdown and tourists and other onlookers were still able to be in the park across the street from the executive mansion.
There was 'heightened security throughout D.C, NBC reported, citing local police officials.
D.C.’s Metro system had increased patrol officers on call for Monday evening’s rush hour, Politico reported.
The attack had an impact on air travel as Boston's main airport was temporarily halted.
'Apparent ground stop for incoming flights to Boston. At least for shuttle flights from NY,' CNN anchor Anderson Cooper Tweeted.
The Federal Aviation Administration later lifted a temporary ground stop that halted inbound flights to Logan International Airport in Boston.
NYPD uniformed officers stand guard in the heart of Times Square
Row of NYPD patrol cars line the streets of Times Square as a show of force
Shine a light: New York loves Boston is beamed on to the side of the Brooklyn Academy of Music building on Monday night
Nuclear power plants in Massachusetts and New Hampshire have increased security as well.
The Pilgrim Nuclear Power Station in Plymouth, Mass., and the Seabrook Station in Seabrook, N.H., heightened checks of vehicles, materials and individuals entering the plants.
Pilgrim, about 45 miles south of Boston, was already shut down for refueling when the explosions occurred. Seabrook is about 45 miles north of Boston in Seabrook, N.H.
Eliot Brenner, a spokesman for the Nuclear Regulatory Commission, said federal officials have not ordered changes in security at other U.S. nuclear reactors in the wake of the Boston explosions.
Organizers from the London marathon — set to take place this Sunday — said they were in contact with Metropolitan Police as soon as the explosion occurred.
'A security plan is in place for the London Marathon. We will be reviewing our security arrangements in partnership with London Marathon,' a police spokeswoman said.
A law enforcement officer stands post at the U.S. Capitol
A police officer patrols the area in front of the Barclays Center in Brooklyn before a Brooklyn Nets NBA basketball game
A police officer with his K-9 companion keeps guard as a Long Island Rail Road train from New York City arrives at a station in Hicksville
Helicopters fly near the construction site of One World Trade Center. Officials in New York increased security after the two bombs at the Boston Marathon were detonated, fearing a copycat attack
'We're stepping up security at hotels and other prominent locations in the city through deployment of the NYPD's critical response vehicles (CRVs) until more about the explosion is learned,' NYPD spokesman Paul Browne said.
Security was increased at the White House and Pennsylvania Avenue has been shut down.
London Marathon officials are reviewing security plans for its race this Sunday.
SCROLL DOWN FOR VIDEO
On the lookout: Police officers on duty at Grand Central Terminal in Manhattan yesterday after New York City heightened its security
Inspection: A US Army soldier inspects a corner in Grand Central Terminal in Manhattan
Close watch: Police officers and a US Army soldier keep a close watch over the busy terminal
A S.W.A.T officer checks planters on a median in a road next to Tufts Medical Center in Boston
'This changes everything [in New York],' one source told the New York Post.
'Everyone’s on high alert. Our marathon was canceled in November. Who knows if that changed someone’s plans?'
TODAY'S POLL
Should Sunday's London Marathon still go ahead after the Boston blasts?
Yes
No
All polls The New York Metropolitan Transportation Authority said the MTA police would increase patrols and bag inspections on the Metro-North and Long Island Rail Road.
The NYPD will give 'additional attention' to the subways as well.
Mayor Michael Bloomberg said security is being upped both visibly and in covert ways, NBC reported.
'We have 1,000 members of the NYPD assigned to counter-terrorism duties, and they - along with the entire NYPD and the investments we have made in counter-terrorism infrastructure - are being fully mobilized to protect our city,' he said in a statement.
A garbage can on a subway platform was seen taped up so that nothing could be tossed inside - preventing a bomb from being placed and left behind.
Standing guard: A Los Angeles Sheriffs Counter Terrorism Unit deputy patrols Union Station before the start of Los Angeles Dodgers game in Los Angeles on Monday
Stop and search: Amtrak Explosive Detection K-9 officer Kenneth Wolf and his dog Teddy ask a passenger to inspect his luggage before boarding a departing train at Union Station in Los Angeles
Bomb squad: Sgt Darryl Judge with the Richland Police bomb squad positions a device next to a briefcase found Monday in Richland, Washington after police received a call of a suspicious package around 2pm
NYPD said it was increasing patrols and security at hotels and other prominent locations until it knows more about the terror attack in Boston
Dozens of uniformed NYPD officers set up in the center of New York City's Times Square following news of the Boston Marathon explosions
A Twitter user posted this picture from a New York City subway platform that shows a garbage can taped up, preventing an explosive device from being tossed inside and left
New York on high alert following Boston blasts
In Washington, the White House increased security outside the building with Secret Service establishing a broader 'perimeter.'
Secret Service spokesman Ed Donovan says the measure was taken 'out of an abundance of caution'. He says it is not unusual to expand or contract the security perimeters.
Shortly after the explosions Monday, Secret Service shut down Pennsylvania Avenue outside the White House, cordoning off the area with yellow police tape.
Several Secret Service patrol cars also blocked off the entry points to the road.
U.S. Secret Service agents stand on top of the White House amid the heightened security around the area (left) along with more squads at Madison Square Garden in New York
A Secret Service officer stands guard in front of the White House after the surrounding area was closed
A couple stands behind a police line on Pennsylvania Avenue in front of the White House
The White House was not on lockdown and tourists and other onlookers were still able to be in the park across the street from the executive mansion.
There was 'heightened security throughout D.C, NBC reported, citing local police officials.
D.C.’s Metro system had increased patrol officers on call for Monday evening’s rush hour, Politico reported.
The attack had an impact on air travel as Boston's main airport was temporarily halted.
'Apparent ground stop for incoming flights to Boston. At least for shuttle flights from NY,' CNN anchor Anderson Cooper Tweeted.
The Federal Aviation Administration later lifted a temporary ground stop that halted inbound flights to Logan International Airport in Boston.
NYPD uniformed officers stand guard in the heart of Times Square
Row of NYPD patrol cars line the streets of Times Square as a show of force
Shine a light: New York loves Boston is beamed on to the side of the Brooklyn Academy of Music building on Monday night
Nuclear power plants in Massachusetts and New Hampshire have increased security as well.
The Pilgrim Nuclear Power Station in Plymouth, Mass., and the Seabrook Station in Seabrook, N.H., heightened checks of vehicles, materials and individuals entering the plants.
Pilgrim, about 45 miles south of Boston, was already shut down for refueling when the explosions occurred. Seabrook is about 45 miles north of Boston in Seabrook, N.H.
Eliot Brenner, a spokesman for the Nuclear Regulatory Commission, said federal officials have not ordered changes in security at other U.S. nuclear reactors in the wake of the Boston explosions.
Organizers from the London marathon — set to take place this Sunday — said they were in contact with Metropolitan Police as soon as the explosion occurred.
'A security plan is in place for the London Marathon. We will be reviewing our security arrangements in partnership with London Marathon,' a police spokeswoman said.
A law enforcement officer stands post at the U.S. Capitol
A police officer patrols the area in front of the Barclays Center in Brooklyn before a Brooklyn Nets NBA basketball game
A police officer with his K-9 companion keeps guard as a Long Island Rail Road train from New York City arrives at a station in Hicksville
Helicopters fly near the construction site of One World Trade Center. Officials in New York increased security after the two bombs at the Boston Marathon were detonated, fearing a copycat attack