Scores of foreign fighters and supporters are abandoning Islamic State and attempting to enter Turkey.
A least one US citizen and two British nationals are part of an exodus reducing numbers in the terror group.
Sources told The Guardian that Stefan Aristidou from London and his wife surrendered to Turkish border police along with Kary Paul Kleman, from Florida, last week.
The three had been living in areas controlled by Isis for two years, but now the capacity of Isis to hold their territory in Iraq and Syria is collapsing.
Turkish officials said the trio surrendered at the Kilis crossing between Syria and Turkey. It is also claimed that Kleman arrived at the crossing with a Syrian wife and two Egyptian women, whose spouses had been killed.
Aristidou has claimed that he went to Syria to live there rather than fight, but was based in Raqqa and al-Bab, which have both fell under Isis control.
Aristidou's neighbours in London said that he started to wear Islamic dress not long before he went missing in April 2015.
Some people have made it across the border into Turkey, however it is not yet clear how many have done so. Others have been caught trying to cross the border.
The UK's Foreign and Commonwealth Office said: “We are in contact with the Turkish authorities following the detention of a British man on the Turkey/Syria border.”
Despite the fact the British woman could face charges, it is believed that she was released from custody.
Aristidou and Kleman may face sentences of between seven and a half and 15 years if they are convicted of terrorism charges in Turkey. The British man could also face charges if he's extradited back to the UK.
Isis sources have confirmed that the group is declining in Syria and whilst many members have contacted their embassies in order to return home, there is a fear that some will use the exodus to infiltrate Turkey and continue into Europe to carry out attacks.