An unknown assailant has killed two assistants to politicians from Poland's main opposition party, the conservative Law and Justice (PiS), in the party's office in the central city of Lodz.

There were conflicting reports of how the man killed his victims and there was no immediate word on his motives.

‘The killer was immediately captured by the police and is now being taken for interrogation,’ Radoslaw Kluska of Lodz municipal police told TVN 24.

First reports said he had shot his victims but police later said he probably used a knife.