Igor Guskov

Ukraine's intelligence services, the SBU, has named a Moldovan, Radu "Rodion" Donciu, aged 43, as a mercenary who has fought for the pro-Russian separatists in eastern Ukraine, and in Syria, with the Russian-led private company, Wagner.

Serbia and Ukraine expressed respect for each other's territorial integrity during a meeting of their presidents on Tuesday that papered over years of tension over Belgrade's refusal to condemn Russian actions in Crimea and the flow of Serbian mercenaries fighting with pro-Russian separatists in eastern Ukraine.

Ukraine security service official Igor Guskov told Ukrainian television on Friday that at least seven Serbian mercenaries were fighting in eastern Ukraine as part of a private Russian military unit, called Wagner, one of whom was now dead.