Malaysian authorities have detained six Thai fishermen for allegedly poaching in the South China Sea off Terengganu, a navy official said Thursday.

Malaysian navy gunboat commander Soo Lin Chai said the vessel came upon the six fishing in Malaysian waters without permits late yesterday near a Malaysian-owned oil rig.

"They did not have any documents," he was quoted as saying by the Bernama news agency.

Soo said the six fishermen were aged between 25 and 40 and from Songkhla in southern Thailand. Their boat is being held by fisheries authorities in Terengganu.