BRUSSELS (AFP).— Two packed commuter trains collided head on during rush hour outside a snow-covered Brussels on Monday killing up to 20 people and injuring 150 amid scenes of bloody chaos, officials said.

The crash left a mass of twisted metal and several carriages on their side, according to witnesses, while an official said doctors were carrying out amputations at the scene.

Passengers covered in blood were rushed on stretchers towards ambulances along the tracks as the snow continued to fall.

"The shock was terrifying. It was terrible," said one of the passengers, who gave her name as Sylvie as she emerged from the crash with an injured arm.

The death tolls varied but just after 1:00 pm (1200 GMT), the Brussels investigating magistrate put the toll at between 18 and 20 dead.

Halle mayor Dirk Pieters told Flemish public television VRT that there are "at least 20 dead."

Scores more were said to be injured with emergency services saying survivors were being treated for shock.

All Eurostar train services between Brussels and London were cancelled as a result of the smash.