British Prime Minister David Cameron is urging his nation's schools to guard against the influence of extremism after three school-aged girls slipped out of the country in a suspected attempt to join the self-declared Islamic State.

The Associated Press reports that Cameron said the teenagers' disappearance was deeply concerning.

"We all have a role to play in stopping people from having their minds poisoned by this appalling death cult," Cameron said.

The latest case involves three girls, aged 15 to 16, who flew from London to Turkey on Tuesday without leaving any messages.

As the BBC reported on Friday:

"The girls were last seen at their homes on Tuesday morning when they gave their families "plausible reasons" to be out for the day, police said.

"They boarded a Turkish Airlines flight, which landed in Turkey on Tuesday evening."

The New York Times says: "Estimates from Europe's counterterrorism coordinator suggest that more than 3,000 Europeans may have traveled to Syria and Iraq since early 2014, and could now represent roughly one-quarter of the foreign fighters in the region."

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