Ten people were killed when a boat carrying 17 passengers sank in rough seas off western Indonesia on Sunday, a navy official said.

The navy spokesman Edi Sucipto said the boat encountered bad weather when it was sailing from the port city of Tanjung Pinang in Riau Islands province east of Sumatra.

"Twelve people have been found, but ten had already passed away," Sucipto told AFP.

He also said two of those 17 people were critically injured. A navy speedboat was still in search of the other five people, who are still missing.

Sucipto added that the stricken vessel was only a small boat which was equipped with an outboard motor.