The children, who were all living in the city of Örebro, were in danger of being brainwashed by adults in Sweden connected to the extremist group Isis, according to a municipal court ruling.
The court heard that the trio, who are all understood to have the same father, were at “very high risk” of being taken abroad by him to either be trained as soldiers or forced into marriage. It ruled that the children should be taken into care by Örebro municipality, in the first decision of its kind in the region.
The move follows a number of similar cases in Gothenburg, in which other children and young people have been placed with social services amid fears that they were also at risk of being influenced by radical groups.
Reacting to the ruling in Örebro, Daniel Norlander, chief secretary to Sweden's national coordinator against violent extremism, Mona Sahlin, told Sveriges Radio that he felt the court had made a “good” decision.
“I find it difficult to express an opinion on the case, but that the municipality is active and uses the tools available to it is something I look at very positively,” he said.
Authorities were alerted to the children's father after he was arrested on suspicion of fraud designed to help fund travel abroad, according to Sveriges Radio. Police later found photos of him posing with guns as part of their investigation.
The case emerged amid ongoing fears about extremism in the Nordic country.
Swedish security service Säpo said last year that more than 125 Swedes were believed to be fighting in Syria and Iraq, of whom 35 are women.
In February it was suggested that around 40 Swedish children under ten are thought to be staying with Isis after their parents joined the terror group.