SIX crew members are missing after the 10,385-dwt general cargo ship Thorco Clouda sank in the Singapore Strait after colliding with a chemical tanker, Reuters reported.

Operated by Danish owner Thorco Shipping and registered in Antigua and Barbuda, the ship had a crew of 12.

Singapore's Police Coast Guard, supported by the Maritime and Port Authority of Singapore (MPA), rescued five crewmen, while the chemical tanker picked up a sixth, the MPA said. 

The accident occurred in Indonesian waters six nautical miles northwest of Batam. The 37,438-dwt Cayman Islands-flagged tanker Stolt Commitment suffered minor damage and was in stable condition.

Indonesian authorities have also commenced search and rescue operations and Singapore is ready to render assistance if required, the MPA said.

The sunken cargo freighter was carrying 560 tonnes of bunker fuel.

"While there are currently no reports of any oil spill, MPA has also put on standby anti-pollution craft," the spokesman said.

The Singapore Strait, one of the world's busiest commercial shipping routes, is a 105-kilometre long, 16-kilometre wide passage between the Strait of Malacca to the South China Sea.