WARSAW, Poland (AP) — Poland's interior minister has apologized after Polish police entered an academic conference devoted to Karl Marx to check if anyone was propagating "totalitarianism" or engaging in "anti-national activity."

Interior Minister Joachim Brudzinski apologized Monday for the incident Friday at a University of Szczecin conference center in Pobierowo, in western Poland.

A conference organizer, Tymoteusz Kochan, said three police officers acting on prosecutors' orders questioned organizers and photographed scholarly publications. Prosecutors confirmed that they ordered the police check.

Kochan, a doctoral candidate in philosophy, said the incident left participants shaken. He said he believed it was an attempt by Poland's right-wing authorities to intimidate them.

Marx was a 19th-century socialist whose views guided the development of communist theory.

Poland's current government is staunchly anti-communist.