Two commuter trains crashed head-on near Brussels during the Monday morning rush hour and at least 10 people were killed, a local official said.
The trains collided in snowy conditions at the village of Buizingen, near Halle, 15 km (9 miles) southwest of the Belgian capital, leading to cancellation of services to France and Britain.
Some passengers were still trapped inside the wreckage several hours after the disaster, which occurred at around 8:30 a.m. (0730 GMT).
The province of Flemish Brabant, which includes the town of Halle, said that the death toll officially stood at 10 with 11 seriously injured, including one child.
There are certainly 10 (dead), but of course that figure could rise, a provincial official said, adding it appeared that one of the trains had ignored a red light.
Earlier, Belgian public broadcaster VRT had quoted the mayor of Halle as saying that at least 20 people had been killed.
Train operator SNCB said it was too early to speculate about the cause of the accident and denied reports it had given a death toll estimate of 25. It said 250 to 300 people were traveling in the two trains at the time.
There are certainly deaths, but it's very difficult to give a precise number at this point. There are people trapped inside, an SNCB spokesman told Reuters.
The two trains were crushed against each other, their fronts suspended in the air. Overhead power lines were severely damaged.
The first two carriages were completely squashed, said 37-year-old Hambaoui Mounir. I was in the carriage right behind. The train fell to one side, people fell over each other, there was no air and women and children were screaming.
A wide range of train services, including high-speed services from Brussels to Paris and the Eurostar from Brussels to Britain via the Channel Tunnel, were suspended for the day.