ALGIERS, Feb. 11-- Twelve people were killed and two others seriously injured in a head-on collision between a bus and a semi trailer in southeast Algeria on Thursday.

An investigation has been opened to find what caused the accident on National Road 6 in the province of Naama, authorities said.

Similar accidents are frequent on the roads linking the north to the south of Algeria. Speeding and the fatigued drivers stand as the main reason for such accidents.

Between 4,000 and 4,500 people die every year in traffic accidents in Algeria, according to official figures.