Authorities in Denmark have charged a Finnish academic with aiding alleged Russian spies in Copenhagen, Finland's national broadcaster YLE has said.

According to RIA Novosti, Timo Kivimäki, 49, was first arrested and questioned by Danish detectives in 2010.

The Finn, who has been suspended from his job as professor of international politics at the University of Copenhagen, admitted to providing consultancy services to four Russian diplomats between 2005 and 2010 and said he had charged some 16,000 euros for the work, the Helsingin Sanomat daily reported.

Denmark's security agency PET says the diplomats were spies.

Kivimäki might have passed information about his students, who the Russians could have then used to recruit agents in Denmark, PET's former head told YLE earlier this week.

But Kivimäki said there was no evidence to back the allegations and insisted that he was "innocent."

He also said he was "relieved" that the matter was going to court.

He faces up to six years in jail if convicted.

Kivimäki has worked in Denmark for many years and has good contacts with radical Muslim and separatist organizations in Southeast Asia, Helsingin Sanomat said.

Finland's security police SUPO said it knew of the investigation. PET could not be reached for comment.

The trial is due to begin on May 8.