By Tom Rayner, Middle East Reporter, Turkey-Syria border
Foreign fighters seeking to join Islamic State are using black-market Syrian passports to enter through Turkish border checkpoints, according to smugglers operating in the area.
It comes as UK police say they now believe three London schoolgirls, who arrived in Turkey over a week ago, have crossed into Syria.
Since last summer, Turkish authorities have banned anyone but Syrian citizens from using official crossings, but Sky News has found that fake documents can be easily purchased from smugglers within hours.
The passports can be made to carry any name or photograph the buyer wishes to use.
The ready availability of such documents, which cost around £500 per passport, underlines the extreme difficulties faced by the Turkish authorities in identifying the true nationality of those entering Syria.
The border crossing at Akcakale, in south eastern Turkey leads to the Syrian town of Tel Abiad, which is under the control of Islamic State.
The area has become a key strategic smuggling route for Islamic State, given its position just 60 miles north of the group's main stronghold in the town of Raqqa.
Two smugglers who make their living bringing people in and out of Syria told Sky News the use of black-market passports was seen as an alternative to cross-border smuggling.
"It helps if they want to go - they have a whole new identity, which can get them across to the other side," one of the men said.
The price for more traditional people-smuggling has recently gone up, due to growing danger posed by coalition airstrikes and the presence of other Syrian rebel groups on the outskirts of the area.
"Before it was 5,000 Syrian pounds (£17), now it's 10,000 (£34] or 15,000 (£51)," he said.
"Before it was possible to cross in one day, now they have to wait two or three days in Turkey, sometimes we stay three days with the people."
But they have also noticed a change in recent months, with more Syrians attempting to leave - claiming they are "afraid" of Islamic State.
Among them are some former IS fighters, who risk being killed if caught trying to defect.
Sky News spoke to a 27-year-old former fighter, who claims he escaped the group before Christmas after being appalled at the beheading of a 14 year-old boy in Raqqah, who was accused of cursing God.
"The brutality was against Muslims," he said.
"I don't disagree they should take harsh measures against non-believers, but now they are behaving with brutality towards fellow Muslims."
He said there was growing division and resentment inside Islamic State between Syrians like himself and the foreign fighters.
"The foreign fighters are given everything - cars, help with marriage, lots of money, but Syrian fighters get very little."
Asked if he had a message for young Muslims in Britain, thinking of following in the footsteps of the three London schoolgirls by heading to Syria, he said: "Go to your homes and stay in your homes. If you want to support the Syrian people, do it with prayer."
