Four children were killed after a train and a school bus collided outside the town of Perpignan in southwestern France on Thursday, the interior ministry said.

Transport Minister Elisabeth Borne described the crash as a "terrible accident" and said on Twitter that she was heading immediately to the scene, more than 850 kilometres from Paris.

"Emergency and public services are fully mobilized," Borne said on Twitter.

The Interior Ministry said seven people in the bus, which was carrying young people between ages 13 and 17, were seriously injured among the 19 aboard.

A spokesperson for SNCF, France's national rail service, said the train carrying 25 people was running at 80 kilometres an hour at the time of the accident. Three of those aboard were slightly injured.

The Pyrénées-Orientales authority tweeted that the collision occurred Thursday afternoon on a railway crossing at a small town some 15 kilometres west of Perpignan, close to the border with Spain. 

French officials did not immediately provide any further details about the crash.

With files from The Associated Press