“My thoughts are with his family, his loved ones and all the staff at who are mourning his loss,” he wrote on X.
French Transport Minister Philippe Tabarot said he was heading to the scene along with the head of France’s state-owned rail operator SNCF.
Tabarot said the collision involved a heavy goods vehicle, while news site Franceinfo reported that it was a truck that had been transporting military equipment.
It said the incident occurred shortly before 07:00 local time (05:00 GMT), citing a local official.
The train had been travelling from Dunkirk to Paris.
The regional rail network, TER Hauts-de-France, said traffic between Béthune and Lens would be disrupted until mid-morning, with services on certain lines resuming gradually.
The BBC has contacted SNCF for comment.
SNCF Chief Executive Officer Jean Castex, who served as France’s prime minister between July 2020 and May 2022, has yet to publicly comment.
Rail union SUD-Rail has called for “total transparency” regarding the incident.