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 US-backed Iraqi forces are trying to retake from ISIS terrorists.
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 ISIS 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 travelled 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.
British Major General Rupert Jones, deputy commander for the Combined Joint Task Force coalition, said on Tuesday the number of foreign fighters travelling to join ISIS 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.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
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