Bangladeshi police say a head-on collision between two passenger buses has killed at least 16 people and injured more than 50 others.

Police say the two buses were traveling on a major highway just outside the capital of Dhaka when they collided early Tuesday.

The cause of the accident was not immediately known.

Prime Minister Sheikh Hasina ordered a probe into the crash, the latest in a series of deadly road accidents in Bangladesh.

On Thursday, 17 people died after a bus crashed into a truck in the Bogra district. And last month, a vehicle carrying school students overturned in the southeastern district of Chittagong, killing 44 people, mostly children.

Traffic accidents kill about 10,000 people in Bangladesh every year. The most common causes are reckless driving, poor road conditions and insufficiently maintained vehicles.