The incident happened outside the town of Perpignan near the Mediterranean coast and the border with Spain, local media reports.

"All emergency services have been mobilized and a crisis-coordination unit set up," the townhall said in a tweet.

At least three fatalities, including three children, have been reported among the bus passengers, according to BFMTV.

Seven others were seriously injured, and two more received light wounds, the local media station added, saying that the victims were school-bus passengers aged between 13 and 17.

The train reportedly hit the rear part of the bus at a railway crossing. French Transport Minister Elizabeth Borne called the crash a "terrible accident" adding that emergency and public services are fully mobilized.

DETAILS TO FOLLOW