BERLIN (Reuters) - German authorities will continue to investigate whether senior Iranian cleric Mahmoud Hashemi Shahroudi committed crimes against humanity, regardless of his location, a spokeswoman said, amid reports he plans to return to Tehran on Thursday.

Shahroudi, the former head of Iran’s justice ministry, has been receiving medical treatment at a clinic in the northern city of Hanover, but plans to leave the country on a flight from Hamburg on Thursday, according to an Iranian opposition group.

The exiled opposition group, the National Council of Resistance of Iran (NCRI), said it had urged Germany to issue an urgent arrest warrant for Shahroudi after learning that the Iranian government had reserved seven flight tickets for him and his entourage on an Iranair flight around midday on Thursday.

An arrest warrant would have to be issued by Germany’s constitutional court.

The group said it filed a formal complaint with prosecutors, accusing Shahroudi of committing crimes against humanity and urging Berlin to prevent the cleric from leaving Germany.

A similar complaint was filed earlier by former Greens lawmaker Volker Beck.

The federal prosecutor’s office said any complaints would be thoroughly investigated. “We will continue to examine on a legal basis whether Mr. Shahroudi was guilty of crimes against humanity, regardless of where he is staying,” a spokeswoman for the prosecutor’s office said.

Javad Dabiran, a spokesman for the Iranian opposition group, said information about Shahroudi’s travel plans came from the Mujahedin-e Khalq (MEK), which was designated as a terrorist group by the U.S. government from 1997 to 2012.

The MEK led a guerrilla campaign against the U.S. backed Shah of Iran during the 1970s, including attacks on U.S. targets. The group, a component of the NCRI, has since renounced violence.

“There is an urgent danger of flight in this case,” Dabiran said.

No comment was immediately available from the Iranian embassy in Berlin.