HANOI, July 25 (Xinhua) -- At least nine people were killed and 16 others severely injured when a sleeper bus overturned in Vietnam's central province of Ha Tinh early Friday morning, Vietnam News Agency reported.

The bus was traveling along National Highway 1 when it lost control, struck a roadside marker and overturned.

It had departed from the capital Hanoi and was en route to the central city of Da Nang when the accident occurred.

Authorities are investigating the case.