Since 2012, 300 people have travelled from Sweden to Syria and Iraq to join Daesh* and other terrorist groups. About 150 of these jihadists (sometimes referred to as "fighters" in the Swedish media) have since returned to Sweden and are keeping a low profile.

The city of Stockholm does not keep track of Daesh returnees who have come back to the capital city after fighting for the terrorist cause in Syria and Iraq, national broadcaster SVT reported.

About half of the 300 jihadists Sweden has produced in recent years are estimated to have returned to Sweden from the Middle East, SVT reported citing Sweden's Security Service (Säpo). Of them, up to 40 have returned to Stockholm, whereas others have returned to Gothenburg, Örebro, Malmö and Borås. However, the Stockholm municipality hasn't contacted a single one of them, despite there being a plan against violent extremism in place since 2016.

PO Hellqvist, a former Säpo chief in Gothenburg, who now works with the police to extinguish violent extremism, found this development "beyond belief".

"This can't be good. The authorities need to know who these individuals are, and there are several reasons to do so. In part, these individuals can be dangerous to society, and some may also need help in order not to become a threat", PO Hellqvist told SVT.

According to SVT, these returnees cannot be brought to justice under the current legislation. However, they can still be a threat and carry on the ideology that spurred them into leaving Sweden in the first place.

"They still carry this mindset. They have violence in mind and can resort to violence in the future. Whether it happens within a week, a fortnight or longer, we don't know", PO Hellqvist said, stressing that while in Syria and Iraq, they may have participated in battles and learned how to handle weapons and explosives.

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This week, SVT published a series of clips from the Middle East reportedly showing jihadists' life under Daesh. In the clips, children as young as three and five years old watch their parents shoot an automatic rifle and brag about killing the "unfaithful".

In the clips, everyone speaks Swedish, and entire families are participating. One of the scenes shows a niqab-clad woman shooting outside of Syria's Aleppo. "Let's watch Mommy do jihad", the woman behind the camera says.

In another scene, a boy gives tips to his father on how to handle his automatic weapon. "Dad, you shouldn't shoot 'drrr', you should go 'ta-ta-ta', otherwise the ammunition will end".

According to PO Hellqvist, authorities should maintain better contact with residents of the so-called vulnerable areas, which he called hotspots of extremism.

"This is fertile ground for this sort of thing, particularly in vulnerable suburbs, and there is a power struggle between various religious groups. We also see how they try to target young people in this sensitive age", Hellqvist said. "Bureaucrats must leave their offices and simply meet people", he concluded.

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Although travelling to Syria and Iraq has all but dried up over the last several years, Säpo estimates the number of Islamists in Sweden has increased sharply. In 2010, there were 200 Islamist extremists in Sweden. In recent years, the figure has grown exponentially to 2,000.

* Daesh (ISIL/ISIS/IS/Islamic State) is a terrorist organisation banned in Russia