TUNIS: Tunisia's security forces called on the government Sunday to take "exceptional measures" to combat the return of extremists fighting for extremist groups abroad.

Tunisia has witnessed a wave of extremist attacks since its 2011 revolution, including on foreign tourists, and the United Nations estimates that their are more than 5,000 Tunisians fighting for extremist outfits, mainly in Iraq and Syria.

"The return of terrorists from hotbeds of unrest in Tunisia is worrying and could lead to the Somalisation of the country," said a statement from the internal security forces' national union.

Battle-hardened fighters "have received military training and have learnt to use all sorts of sophisticated weapons," it added.

The warning came a day after Tunisian authorities said they had arrested three people including the nephew of Anis Amri, a national suspected of carrying out a deadly truck attack on a Berlin Christmas market this week.

Hundreds of people gathered outside parliament in Tunis Saturday to protest against letting extremists back in the country.

President Beji Caid Essebsi said earlier this month that Tunisia would refuse to pardon Tunisians who fight for extremist organisations.

"Many of them want to return, and we can't prevent a Tunisian from returning to his country," he told AFP, "but we will be vigilant."

Following a storm of criticism in the press and on social media, on Dec. 15 he told Tunisian local television that "we will not be indulgent with the terrorists".

On Friday evening, the country's Interior Minister Hedi Majdoub told parliament 800 Tunisian nationals who had fought for extremist groups abroad had since returned to the country.