A British man fighting in Ukraine has been captured by pro-Russian separatists, an international legion backing the Kyiv government said on Wednesday."It was announced in the Ukrainian press that the Russians had completed a criminal investigation against three foreigners whom they were preparing to put on trial and that they risked the death penalty," Damien Magrou, spokesman for the International Legion for the Defence of Ukraine (LIDU) told AFP."One of the three names mentioned in the article, Andrew Hill, is a legionnaire who has a contract with the Ukrainian army," he added.Magrou stressed that under the Geneva Convention Hill should be considered a prisoner of war, and treated as such.According to the LIDU, Hill has been held "in captivity for some weeks" by pro-Russian separatists in eastern Ukraine."Executing prisoners is a war crime," it said.Pro-Russian officials have suggested in recent weeks that captured Ukrainian soldiers, including those from the nationalist Azov regiment, could face trial and the death penalty.A moratorium on the death penalty has been in place in Russia since 1997, but this is not the case in the two separatist territories of eastern Ukraine.Four foreign military volunteers have already been killed while fighting the Russian invasion of Ukraine, according to the LIDU, the official body for foreign volunteer fighters.The international legion had given the names of a Dutchman, an Australian, a German and a Frenchman, without specifying the date or circumstances of their death. On Wednesday Magrou, said the Frenchman was from the northern region of Normandy and that he died in an artillery strike.Russia claimed this week that it had killed "hundreds" of foreign fighters in Ukraine since the start of its invasion in February.