A British judge on Friday barred five teenage girls from travelling abroad amid concerns they would go to Syria to join Islamist fighters, in the second such ruling this week.

High Court judge Anthony Hayden made the girls from east London -- two aged 15 and three aged 16 -- "wards of court", a legal move that prevents them leaving England and Wales.

He confiscated their passports and also those of a number of adults involved in caring for them, noting that in at least one other case a young girl travelled on a relative's passport.

In a ruling prompted by an application by the local authority, Tower Hamlets in east London, Hayden said that despite signs the teens were becoming more radical, their relatives were not cooperating with social services.

"It seems to me that that must have been known to the parents and they deliberately did not share it with the authorities who were keen to protect these vulnerable young girls," the judge said.

He acknowledged his ruling was a "draconian" step, but said: "The risk contemplated here is as grave as it can be for it is common knowledge that so many have lost their lives in Syria and so many have gone knowing that would be likely."

Earlier this week, Hayden imposed a similar ruling on a 16-year-old boy amid fears he would follow his three brothers in joining Al-Qaeda linked fighters in Syria.

Two of the brothers have been killed, and the other wounded.

"Sometimes the law has to intervene to protect these young people, ultimately from themselves," the judge said Friday.

The British authorities are increasingly concerned by the numbers of young people heading to join jihadists in Syria, after a string of high-profile cases in recent weeks.

Three schoolgirls from London followed a classmate to Syria earlier this year by travelling through Turkey, while three teenage boys and a 21-year-old woman were stopped in Turkey in the past week on suspicion of trying to cross the border.

About 700 people are thought to have gone to Syria from Britain, of whom almost half are reported to have returned.