An unknown man suffered serious injuries and was in coma at the Patra hospital following a gang attack on Sunday night, according to local reports.
The victim, who is said to be an illegal immigrant, was assailed by a group of men on motorbikes. He was rescued by people who were watching a play at a nearby theater.
Witnesses have identified one of the assailants as a local member of the far right Golden Dawn party, according to a local newspaper.
Brutal attacks against migrants in Greece are becoming almost a daily occurrence, with violent mobs acting almost unhindered as police have failed to make any significant arrests.
Police in the western port city of Patra on Tuesday arrested a 31-year-old man in connection to a brutal attack on an undocumented migrant on Sunday night that left the victim in a coma after he suffered extensive head injuries.
The 31-year-old is suspected of having assaulted — together with another two men who are being sought by authorities — the Tunisian migrant, who has not been named.
They beat him viciously using their fists and feet, until a crowd from a nearby theater chased them off and called an ambulance to the scene.
Witnesses had identified one of the three assailants as belonging to the far-right Golden Dawn group