Thirteen people were killed and up to 50 injured when two trains collided in Chalupki in southern Poland Saturday, emergency services said.

The cause of the head-on collision, which Transport Minister Slawomir Nowak, speaking to television station TVN24, described as one of the worst railway accidents of the last few years, was not immediately clear.

TVN24 quoted emergency services as saying 13 people had been killed and up to 50 had been injured. Some 450 firefighters and 100 police officers were working at the site.

(Reporting By Karolina Slowikowska; Editing by Myra MacDonald)