Three schoolgirls have fled the UK in a suspected bid to travel to Syria and join ISIS (Daesh).
Shamima Begum, 15, Kadiza Sultana, 16, and an un-named 15-year-old, all from east London, flew to Istanbul, in Turkey, from Gatwick airport on Tuesday without leaving any messages behind for family or friends.
Scotland Yard detectives urgently appealed for information about the missing girls, who all go to the Bethnal Green Academy school and were described as 'straight-A students'.
Commander Richard Walton, head of the Metropolitan Police's counter terror command, said the runaways are good friends with another 15-year-old girl who fled to Syria in December.
He said the force was becoming 'increasing concerned' about a growing trend of young girls showing an interest or intent in joining IS, an organisation now notorious for its barbaric treatment of hostages and oppression of women.
But Mr Walton added the teenagers' families were 'devastated' but there was a 'good chance' the girls were still in Turkey.
The youngsters, who police fear may be heading to join terror group Islamic State, are all pupils at the same school and are close friends, police said.
They were last seen at their homes on Tuesday morning when they gave their families 'plausible reasons' to be out for the day. They were reported missing later that day and on Wednesday morning.
The girls met at Gatwick where they got on a Turkish Airlines flight which landed in Turkey on Tuesday evening.
Mr Walton said: 'We are extremely concerned for the safety of these young girls and would urge anyone with information to come forward and speak to police. Our priority is the safe return of these girls to their families.
'We are reaching out to the girls using the Turkish media and social media in the hope that Shamima, Kadiza and their friend hear our messages, hear our concerns for their safety and have the courage to return now, back to their families who are so worried about them.'
Shamima is possibly travelling under the name of Aklima Begum, 17, police said. The third girl is not being named at the request of her family.
Mr Walton added: 'We are concerned about the numbers of girls and young women who have or are intending to travel to the part of Syria that is controlled by the terrorist group calling themselves Islamic State.
'It is an extremely dangerous place and we have seen reports of what life is like for them and how restricted their lives become.
'It is not uncommon for girls or women to be prevented from being allowed out of their houses or if allowed out, only when accompanied by a guardian.
'The choice of returning home from Syria is often taken away from those under the control of Islamic State, leaving their families in the UK devastated and with very few options to secure their safe return.
'If we are able to locate these girls whilst they are still in Turkey, we have a good possibility of being able to bring them home to their families.'
Police said Shamima was 5ft 7in tall, and wearing black thick rimmed glasses, a black hijab, light brown and black leopard print scarf, dark red jumper, black trousers and jacket, carrying a dark blue cylindrical shape holdall with white straps.
Kadiza is 5ft 6in tall, of slim build and wearing black-rimmed glasses, a long black jacket with a hood, grey striped scarf, grey jumper, dark red trousers, carrying a black holdall.
Both are British nationals, speak English with London accents and also speak Bengali.
The third girl is 5ft 6in, of slim build, wearing black thick rimmed glasses, black head scarf, long dark green jacket with fur lined hood, light yellow long sleeved top, black trousers, white trainers carrying a black Nike holdall. She speaks English.
Scotland Yard stressed the appeal was not about 'criminalising people, it is about preventing tragedies by offering support to the young and vulnerable'.
The appeal comes after it was claimed that Muslim extremists are offering teenage girls in the UK money to marry Islamic State militants in Syria and Iraq.
ISIS supporters are believed to be offering cash incentives to encourage schoolgirls to travel to the group's de facto capital Raqqa and marry fighters.
It was reported in December that ISIS channels money for travel expenses through international money wire systems, enabling the group's UK cell to offer significant sums of cash to disenfranchised teenagers.
© Associated Newspapers Ltd.