An Auckland man who was discovered dead in his sleepout yesterday died from head injuries, police say.

Police have launched a homicide investigation into the death of the 55-year-old Manurewa man after the discovery of his body in a converted garage, where he lived.

They believed he was attacked while he was in the sleepout, which was behind the main house.

He was found by one of his flatmates about 10am at their Great South Road property.

Police were appealing to the public and the local Manurewa community to come forward with any information of suspicious activity seen at or in the vicinity of 217 Great South Road.

Information on any activity in or around this address between Thursday morning and Friday morning was of particular interest to police.

The victim's address was close to a busy intersection at Weymouth Road and Great South Road.

A team of police was canvassing the area talking to residents and members of the community.

Police urged anyone who had information that would assist them to call Counties Manukau Police on 09 261 1300 or call Crime Stoppers anonymously on 0800 555 111.