A man has died from his injuries after an assault overnight in Auckland.

The man, in his sixties, was assaulted on Great South Road in Papakura at about 2.30am, police said. He was critically injured and taken to Middlemore Hospital but died this morning.

The police say two people had been identified as witnesses and another person was helping them with their inquiries.

In another incident, a man had a heart attack after a fight on Bairds Road in the suburb of Otara at about 3am.

He was in a serious condition in hospital, police said.