The Countdown security guard who died from his injuries allegedly after a single punch to the head has been named.

Goran Milosavljevic was a Serbian national who had worked at the Papakura store for eight months.

He was allegedly felled by a single punch to the head by a young man after Milosavlijevic approached him, suspicious of his behaviour.

He died this morning of his injuries, police said.

A teenager charged with manslaughter over the incident has been granted interim name suppression.

The teen appeared in Papakura District Court this afternoon where Judge Jane Lovell-Smith said he would be remanded in custody until he could appear before the High Court on May 23.

Counties Manukau South area commander Inspector Dave Glossop confirmed to the Herald earlier today that police were investigating the death.

"On May 2, police were made aware of an incident at a supermarket in Papakura where a security guard was assaulted," he said.

"The victim was taken to Middlemore Hospital but sadly died in hospital early this morning from his injuries."

Glossop said police were supporting the victim's family who were not in New Zealand.