A search is underway in the southern ocean for a Southern Lakes Helicopters helicopter that has gone missing near the Subantarctic Islands.

The machine had responded to a private medical evacuation from a boat and was last heard from at 7.37pm last night near Yule Island, a small island near the northern part of the Auckland Island group and a search was now being coordinated around that area.

Rescue Coordination Centre NZ (RCCNZ) spokesman Mark Dittmer said three people were on board the helicopter.

RCCNZ issued a mayday call to boats in the area last night and five fishing boats were already searching, he said.

A Royal New Zealand Air Force P3 Orion with specialist equipment had also been dispatched to the area to try and locate any sign of the missing helicopter.

The boat with the injured person on board was proceeding to Bluff for medical assistance,