The UK Foreign Office on Friday summoned Russian ambassador Andrey Kelin to Downing Street after Moscow-backed separatists revealed Paul Urey, a British man captured by pro-Russian forces in Ukraine, had died in detention.
“I am shocked to hear reports of the death of British aid worker Paul Urey while in the custody of a Russian proxy in Ukraine," said UK Foreign Secretary and Conservative leadership candidate Liz Truss.
"Russia must bear the full responsibility for this. Paul Urey was captured while undertaking humanitarian work. He was in Ukraine to try and help the Ukrainian people in the face of the unprovoked Russian invasion.
"The Russian government and its proxies are continuing to commit atrocities. Those responsible will be held to accountable. My thoughts are with Mr Urey’s family and friends at this horrendous time.”
Her condemnation came after Darya Morozova, a representative of the self-proclaimed Donetsk People's Republic, disavowed responsibility for the death.
"He died on July 10," she said on messaging app Telegram, adding that he had diabetes.
Non-governmental organisations describe Urey as a humanitarian aid worker in Ukraine. However, Moscow-backed separatists are insisting he was a "professional" soldier and took part in conflicts in Afghanistan, Iraq, Libya and Ukraine.
Ms Morozova said that the Briton took part in fighting in Ukraine and had also recruited and trained mercenaries before his capture in April.
Urey, born in 1977, was a Type 1 diabetic and needed regular insulin doses, according to his mother Linda Urey, who had earlier said his family was "extremely worried".
Ms Morozova said he suffered from a number of chronic diseases and was also "in a depressed psychological state".
"Despite the severity of the alleged crime, Paul Urey was given appropriate medical assistance," she said.
"However, taking into account his diagnoses and stress, he died on July 10."
Ms Morozova also accused the International Committee of the Red Cross of refusing to provide him with necessary medicine.
According to humanitarian organisation Presidium Network, Urey was a well-travelled humanitarian who worked for eight years in Afghanistan.
Pro-Russian separatists have captured a number of foreign citizens whom they describe as mercenaries.
Among them are Britons Aiden Aslin and Shaun Pinner who last month were sentenced to death by separatist authorities in the Ukrainian stronghold of Donetsk.
