Fears over 20 fishermen after their boat overturned in Sea of Japan

A life raft with six Russians and four Indonesians was rescued by a passing cargo ship, the  Anatoly Torchinov, which also reported the fishing boat had overturned. But 20 more men remain unaccounted for in chilly waters. 

Intensive air searches are due to resume at first light and other ships are assisting in the search. 

The reason the fishing vessel overturned is not yet clear. 

Rescue services said no SOS was heard from the stricken boat. The search operation involves four ships and an An-24 aircraft.

The vessel's home port is Nakhodka in the Russian Far East.  Its crew comprised 19 Russians and 11 Indonesians. 

'No SOS signals came from the boat, its emergency buoy was silent,' said the regional department of the Russian Emergencies Ministry. 

'At a request from the boat's owner, an An-24 plane from the Far Eastern rescue centre was sent to the area. It surveyed an area of 2,600 square nautical miles'. The rescued men are heading for the port of Kholmsk in Sakhalin region.