Two among a group of British medical students, who have travelled to Islamic State-held territory to provide aid, are brother and sister, it is believed.
Concerned families of the group of up to 12 medical students have arrived in a temporary camp at a hotel on the border with Turkey, with some saying they will not go home until their loved ones have been returned.
The students are reported to have sent messages to their families, confirming their wellbeing, but have not divulged their location.
They are all of Sudanese heritage, the majority UK citizens. Some are recent graduates while others are still studying at medical school in Khartoum.
The siblings were named as Tamir and Logain by Turkish politician Ali Ediboglu, who is helping the parents locate their children. Their surname has not been revealed.
Tamir and Logain were not included in the original list presented by the politician. It is now believed two of those initially named may actually be of other nationalities.
The medics flew from Sudan to Istanbul, where they took a bus to the Turkish/Syrian border, and are reported to have crossed into Islamic State territory on March 14.
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The worried parents began arriving in Turkey the same day, following a tip off from one of the students, who told her sister she was traveling to Syria.
“Don’t worry about us, we’ve reached Turkey and are on our way to volunteer helping wounded Syrian people,” medical student Lena Maumoon Abdulqadir wrote, but her parents believe she is working for a jihadi group, probably the so-called Islamic State.
When her father attempted to stop her leaving, he alerted a number of other British Sudanese families with children in Khartoum. They soon discovered other families had children in the group of medics.
The British Foreign Office says it is providing assistance to the families encamped at the border. The Home Office said the medics would not necessarily be prosecuted upon their return if it could be proved that they were not fighting.
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“We are providing consular assistance to families of British nationals who are believed to be missing after traveling to Turkey,” a Foreign Office spokesman said. “We are also working closely with the Turkish police to try to establish their whereabouts.”
Ediboglu criticized the Turkish government for not intervening sooner.
“The kids are sending messages to the families every day saying ‘don’t worry about us, we are working, we are fine.’ It shouldn’t be hard for the Turkish National Intelligence Service to track their phones.”
“But they are taking things slow. Unfortunately we haven’t seen any support from our government yet. They didn’t help and I have the impression that they don’t care at all. But we are not going to give up looking for them, especially me,” he said.