London: As many as 20 children, including a one-year-old boy, have been taken into state care in the UK over their parents' alleged links with the Islamic State (ISIS) terrorist network, a media report said on Sunday.

The children were placed in foster care or with relatives and in some cases reunited with their families only on condition that the parents wear an electronic tag to deter them from fleeing to Syria, 'The Sunday Times' reported.

The newspaper's investigation focuses on British youngsters who have been exposed to extremism by their families.

It analysed hundreds of pages of transcripts from nearly a dozen cases heard by the secretive family courts in Britain relating to Syria. The findings raise fears of what has been dubbed "Generation Jihad" of radicalised children in the UK.

In one case, a two-year-old boy who was taken to Syria by his mother to live under ISIS reportedly showed a marked interest in guns and "shooting people" on his return to Britain.

The boy, who cannot be identified for legal reasons and is referred to as "Y", was made to pose alongside an AK-47 assault rifle and dress in ISIS-branded clothing for propaganda during his brief stay in Raqqa, the defacto capital of ISIS. He was assessed by a social worker and a doctor on his return to Britain in 2015.

In a judgment later handed down at the Royal Courts of Justice in London, Justice Russell said: The evidence of the social worker is that Y is all too aware of what a gun is and becomes overexcited by the suggestion of guns and shooting, and runs around mimicking shooting and makes noises of gunfire.

The boy, who is now four, has been removed from his mother and lives with a grandparent. He is among a small number of British children who have come back from Syria so far, although British officials are expecting an influx as ISIS gets defeated in its main strongholds.

In details of some of the other cases unearthed in the report, a young girl from Yorkshire was made to chant a pro-jihadist mantra linked to Osama bin Laden by her parents and the court was told that her mother's phone pin code was 0911 in reference to the September 11, 2001 attacks on the World Trade Centre in New York.

A young girl from east London who was prevented from boarding a Syria-bound flight by counter-terror police had allegedly watched so much terrorist propaganda that she became "immune to brutality and death".

"She gave some of the most disturbing evidence I have ever heard from a child or, for that matter, an adult, said Justice Hayden, who presided over her case.

"She told me how violent beheadings, point-blank shootings through the brain and images of mass killings no longer had any impact on her, he said.

More than 100 British women are believed to have travelled to the Middle East to join jihadist groups, many with young children. The court papers, however, indicate that many children who never even made it to Syria are still of concern.