At least 21 people have died and more than 20 others are missing after a passenger ferry sank off western Myanmar, officials say.

Rescuers saved 167 people after the boat was hit by huge waves off the coast of Rakhine state, they said.

Officials said 209 people were on board, though residents were quoted as saying that there could have been many unregistered passengers.

Ferry sinkings are common in Myanmar, also known as Burma.

The boat was travelling to Sittwe, the capital of Rakhine state, when it capsized near Myebon, officials said.