(reuters) -- The imam's residence permit was withdrawn as a prelude to expelling him. He had lodged an appeal against that decision which, if it failed, would oblige him to leave the country, Minister Theo Francken told radio station BelRTL.

Brussels' Grand Mosque, which was leased to Saudi Arabia for 99 years in the 1960s as part of an energy deal, has faced repeated accusations from local politicians of propagating ultra-conservative forms of Islam.

"There is a problem with the Grand Mosque... I have taken the decision to withdraw the residence permit of the imam of that mosque," Francken said.

"We have had some very clear indications that he was very radicalised, Salafist and conservative. He was dangerous for our society and national security."

Francken did not name of the imam, who the ministry also declined to name when contacted by Reuters.

Authorities at the mosque were not immediately available for comment.

The Salafist movement - which is strongly influenced by Saudi Arabia's Wahhabi school of Islam - sees many other branches of the faith as heretical has been linked to militant groups such as Isis.

A judge will decide in the coming weeks on the imam's appeal.