An Irish convicted killer who was allowed to enter Australia from Ireland despite serving three years in jail at home is now wanted by NSW Police over a stabbing and a separate one-punch assault in Sydney.

Patrick Farrell, 29, is being sought over the stabbing in Randwick last month which left 30-year-old Oliver Solan with a partially severed ear. Police also want to speak to him in relation to an assault on a man at Matraville in November last year.

Farrell was 21 when he was jailed in Ireland for three years in 2013 for killing a 20-year-old man he assaulted as the victim pleaded not to be hit.

CCTV evidence shown to Mullingar Circuit Criminal Court showed victim Andrew Dolon putting his hands out begging "please don't hit me" before Farrell hit him twice, critically injuring him. Mr Dolan died in hospital soon after.

In Sydney last year, a 56-year-old man was allegedly punched in the beer garden of a hotel in Matraville, knocking him unconscious.

Police allege footage shows Farell and the victim in a verbal argument before the older man stands up and is allegedly hit by the Irishman with a left-handed punch which put him in hospital for two days.

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And in August, police allege Farrell was with a number of people when they were involved in an attack on Mr Solan.

Farrell is described as 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.

Anyone who may have information that can assist investigators are urged to contact Maroubra Police Station on (02) 9349 9237 or Crime Stoppers on 1800 333 000.

Originally published as Irish killer allowed into NSW now wanted over brutal attacks