Nine British medical students and doctors are feared to have travelled to Syria to work in areas controlled by Islamic State militants.

The group, all in their late teens or early 20s, had been studying medicine in Sudan.

Some of their relatives, who have travelled to the Turkish-Syrian border, told the BBC they were gravely concerned about their welfare.

The medics are believed to have entered Syria more than a week ago.

They have been named as Lena Maumoon Abdulqadir, Nada Sami Kader, Rowan Kamal Zine El Abidine, Tasneem Suleyman Huseyin, Ismail Hamadoun, Tamer Ahmed Ebu Sebah, Mohamed Osama Badri Mohammed, Hisham Mohammed Fadlallah and Sami Ahmed Kadir.

BBC Turkey correspondent Mark Lowen said some in the group had sent messages to their parents saying they were doing voluntary work to help Syrians.

BBC correspondent, who described the group as British-Sudanese, said their families had travelled to Gaziantep in southern Turkey to try to find them.

One of the fathers said he was not getting enough support from British and Turkish authorities and did not understand how Turkey allowed such a large group to cross the border.

A Foreign Office spokesman said: "We are providing consular assistance to their families and we have informed the Turkish police to try and ascertain their whereabouts."

The nine Britons are understood to have been joined by two Sudanese medics, one who is American-Sudanese and one Canadian-Sudanese.

The Observer newspaper reported that the students' parents believed they were in Tel Abyad and wanted to work with IS, but they were almost certain they did not plan to take up arms.

The medics are said to have been born in England but were sent to Sudan to study and experience "a more Islamic culture".

A Home Office source told the paper the medics would not automatically face prosecution under anti-terror laws if they returned to the UK if they could prove they had not been fighting.