Two trains crashed head-on outside of Brussels on Monday, killing at least 20 people, officials and Belgian broadcaster VRT said.
The local trains collided near Halle, some 15 kilometres (9 miles) southwest of Brussels at around 8:30 a.m. (0730 GMT).
VRT said 20 people were killed, but officials from the train line operator were unable to immediately confirm that figure.
Train services, including the high-speed line between Brussels and Paris, were blocked.
