Irishman, 29, wanted over two shocking alleged assaults is arrested three weeks after police launched manhunt - as it's revealed he was allowed into Australia despite KILLING a man back home

Patrick Farrell spent three years in jail for the violent death of 20-year-old student Andrew Dolan in Ireland in 2011

An Irish one-punch killer has been arrested in Sydney three weeks after police issued an appeal to track him down over two alleged violent assaults.

Patrick Farrell, 29, was allegedly involved in attacking Oliver Solan, 30, and leaving him barely conscious with part of his ear severed in the hallway of a Randwick apartment block on August 29.

Farrell is also accused of knocking a 56-year-old man unconscious in a beer garden in Matraville in the city's eastern suburbs last November.

The 29-year-old was arrested on Wednesday in Parramatta and was walked in handcuffs to Parramatta Police Station. 

He was charged with wound person with intent to cause grievous bodily harm and assault occasioning actual bodily harm over the two alleged offences.  

Farrell has already spent three years in jail for manslaughter after punching Andrew Dolan, 20, in the Irish town of Mullingar, west of Dublin, in December 2011.

'Don't hit me,' Mr Dolan had begged. 'What did I do?' 

Farrell was arrested at his lawyer's office on George Street, Parramatta and then marched 100m up the road to the police station, The Daily Telegraph reported.

The convicted killer allegedly lied on his visa application about his criminal history to get into Australia.

Neighbours found victim Oliver Solan, 30, barely conscious in a hallway at a Young Street apartment block in Randwick, in Sydney's east, about 8.40pm on August 29

Patrick Farrell (left on left and right on right) was arrested on Wednesday in Parramatta three weeks after police launched an appeal to track him down

'We have an important job to do which is find him,' NSW Police Commissioner Mick Fuller told 2GB last week. 

Mr Dolan's father Joe earlier this month said he was horrified by the new allegations.

'We are shocked and appalled, these allegations are very serious,' he said from his home in Ireland.

'We wonder how he got to Australia in the first place and hope justice will be delivered appropriately.'

His son, a young biomedical student, pleaded for his life before Farrell delivered the fatal blow.  

Patrick Farrell spent three years in jail for the violent death of 20-year-old biomedical student Andrew Dolon in Mullingar, Ireland in 2011 

He died in hospital ten days later.

Farrell, then 21, pleaded guilty to the unlawful killing.

In campaigns to end one-punch violence, Mr Dolan's mother Rosie said if bystanders had intervened, her son may still be alive.

According to the Australian Department of Home Affairs' website, all visa applicants have criminal record checks.

The website also says that anyone who has had a jail sentence of more than one year is banned from entering Australia.

Home Affairs Minister Peter Dutton's office said it could not comment on individual cases. 

Mr Dolan (pictured left) died in hospital ten days later. Farrell pleaded guilty to killing Mr Dolan

In his latest alleged attack on August 29, Farrell and his co-accused allegedly left Oliver Solan in a pool of his own blood in the corridor in a Randwick apartment in Sydney's east. 

The 30-year-old was left with a severed ear and a punctured spleen, which later had to be removed. 

Two others who were involved in Mr Solon's attack have been charged. 

Farrell also allegedly knocked a 56-year-old man unconscious in a beer garden in Matraville, also in Sydney's east, in November last year.

Police allege security footage from the venue showed Farrell and the victim in a verbal argument before the the Irishman allegedly delivered the left-handed blow. 

The other man was in hospital for two days.

Farrell is about 175cm tall, of medium build, with brown hair and brown eyes.

He is known to frequent the areas of Randwick, Maroubra, Mascot and Alexandria. 

The Irishman allegedly hit him with a left-handed punch that knocked him unconscious 

Security officers helped the pub patron who fell flat on his back before being taken to hospital for two days