LONDON (Reuters) - Two British medics who abandoned studies in Sudan to join Islamic State with a group of other students have been killed in fighting in Iraq, the BBC reported on Wednesday.

Ahmed Sami Khider and Hisham Fadlallah died at the weekend, the BBC said, with Khider believed to have been killed in a convoy as it left the city of Mosul, which U.S.-backed Iraqi forces are trying to retake from IS militants.

Britain’s Foreign Office said it was unable to confirm the deaths.

The two men had been part of a group of nine mainly British-Sudanese medical students from Khartoum’s University of Medical Sciences and Technology who had joined IS in 2015. Five other Britons from the institution joined them soon afterwards and at least four had now been killed, the BBC said.

Security services estimate some 850 Britons have traveled to Syria or Iraq, and a number of these are reported to have been killed, including two deliberately targeted in drone strikes because they were believed to be plotting attacks on Britain.

Last week, British citizen Abu-Zakariya al-Britani, who had been given compensation by Britain for his detention in the Guantanamo Bay military prison, blew himself up in a suicide bomb attack on Iraqi forces.

British Major General Rupert Jones, deputy commander for the Combined Joint Task Force coalition, said on Tuesday the number of foreign fighters traveling to join IS had dropped by between 75 and 90 percent, because it was harder to reach Iraq and Syria and the reality of going there had made it unappealing.