Two Irish men have been charged with murder, after allegedly fatally assaulting a 66-year-old man they did not know outside their inner west share house.

Police and NSW Ambulance were called to the corner of Liverpool Road and Grosvenor Crescent in Summer Hill just after midday on Saturday, December 29, finding 66-year-old Paul Tavelardis suffering critical injuries by the side of the road.

Mr Tavelardis was taken to Royal Prince Alfred Hospital in Camperdown in a critical condition, where he died on Monday morning.

Christopher McLaughlin, 24, and Nathan Kelly, 21, were arrested in Summer Hill shortly after the assault and taken to Burwood Police Station, where they were charged with reckless grievous bodily harm in company and affray.

Police say that they did not know Mr Tavelardis.

The pair hail from Glengad in Ireland's north, and had only been in Australia for several months prior to the alleged assault, according to local media reports.

On Tuesday, their charges were upgraded to murder after Mr Tavelardis died.

The two men were refused bail by Parramatta Bail Court on December 29, and will appear at Burwood Local Court on Wednesday on charges of murder.