PARIS - At least four students were killed and 24 seriously injured, including 21 students, on Thursday after a train collided with a school bus in Millas, southern France, local television channel BFMTV reported.

The accident took place at about 16:00 local time (1500 GMT) at a railroad crossing when a TER train struck the back part of the school bus which was transporting students aged 13 to 17 years old, BFMTV said.

Four students lost their lives, seven others were seriously wounded and 12 suffered from minor injuries. All the victims were students, reported BFMTV.

The cause of the accident was not identified yet.

"Very strong emotion following the terrible accident occurred at Millas in the Pyrenees-Orientales. Rescue and the state's services are fully mobilized. I go there immediately," tweeted Transport Minister Elisabeth Borne.