At least 38 people have been killed after a passenger ferry with 173 on board capsized in rough waters in the central Philippines.

Rescue boats picked up dozens of survivors who clung to the overturned hull of the Kim Nirvana, one kilometre from Ormoc port, Ciriaco Tolibao from the city's disaster risk reduction and management office told AFP.

Divers were scouring the murky waters searching for survivors from the inside of the ship, he said.

A report on Manila radio said 21 people were missing. However Tolibao could not say how many were still missing or had been rescued.

The coast guard confirmed that it was engaged in search and rescue activities but could give no further details of the operation.

Poorly-maintained, loosely-regulated ferries are the backbone of maritime travel in the sprawling archipelago.