A Belgian minister drew criticism Friday for asking officials to survey how many people might be turning into Islamist extremists by looking at factors including whether they have grown beards.

Rachid Madrane told AFP he had emailed some 700 officials in the French-speaking part of Belgium who deal with parole or community service issues to give an inventory of all changes in attitudes in people they handle.

These included wearing clothes that adhere to rules in the Koran, stopping shaking hands with women, abandoning pastimes or hobbies or sporting new facial hair, according to the email.

Belgian authorities said in January they had broken up a major Islamist cell that was planning to kill police officers in public places following a series of terror raids in which two suspected jihadists were killed.

But Xavier Lorent, an official with Belgian's largest union, the CSC, criticised the move.

"It's not the role of justice assistants. They are not going to turn into police informers," Lorent said, adding the criteria were "subjective" and targeted "only one kind of radicalism."

The minister admitted there was "some clumsiness" in the move but told AFP that "I don't want to turn these justice assistants into informers."

He added the goal is to "know the extent of the phenomenon" of radicalisation in order to organise training for the assistants.

Belgium is the EU country with the largest number of jihadists travelling to Iraq and Syria relative to its population, experts say, with 300 to 400 young Belgians in a country of only 11 million people.

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