British police yesterday said they believed that three London schoolgirls who travelled to Turkey and are thought to be trying to join militant Sunni Islamist group Islamic State, have now crossed into Syria.

Friends Amira Abase, 15, Shamima Begum, 15, and Kadiza Sultana, 16, flew to Istanbul from London on February 17.

Police gave no further details but said they continued to work closely with Turkish authorities on the investigation.

The girls’ plight has prompted widespread concern in Britain, with Prime Minister David Cameron urging social media firms to do more to deal with online extremism saying the girls appeared to have been radicalised “in their bedrooms”.

He also said airlines needed new systems to vet children travelling alone.

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