Four people, including two teenagers aged 12 and 15, were killed after a train hit a school minibus in northern Belgium on Tuesday, the country's deputy prime minister said.

The bus carried seven students, a driver and a supervisor at the time of the collision. The other five students on board were sent to hospital in critical condition but are now all said to be stable, local media reported, citing a police spokesperson.

Police said the barrier at the crossing was down and the light was red when the collision happened. An investigation into how the crash happened is ongoing.