John Harding said he suffered a fractured sternum, damage to his coccyx, broken ribs and neurological damage to his hand in the holding centre in Donetsk.
A freed British prisoner of war who was held by Russian-backed separatists has told Sky News how he was tortured over several days.
John Harding said he was used as a “punching bag” by the guards in a holding facility in the self-declared Donetsk People’s Republic in eastern Ukraine.
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The centre was run by the MGB, which he said was the equivalent of Russia’s FSB, formerly the KGB.
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He said he was held there for about nine days in a small cell about 4ft by 6ft, between being taken to the prosecutor’s office for questioning.
Mr Harding was one of five Britons freed in recent days in a prisoner swap with Russia. He is now back in the UK after his release with the help of the Ukrainians and the Saudis.
Shaun Pinner (centre) and Aiden Aslin (right). John Harding has his thumb up
Image: Mr Harding, left, with fellow POWs Shaun Pinner and Aiden Aslin on a plane after their release
Mr Harding had been in Ukraine teaching its soldiers how to use first aid kits.
When the Russians crossed the border in the February invasion, they were near his base and he ended up in the Azovstal steel complex, where he and his colleagues fled because it was a good defensive position with underground tunnels.