Ukrainian noncombatants have been held by Russian forces for months following its invasion. Some are deemed to be prisoners of war, even though they never took part in the fighting. Others are in a sort of legal limbo - not facing any criminal charges or considered to be POWs. Ukraine's top human rights organisation, the Centre for Civil Liberties, has counted some 900 civilians captured by Russia since the war began, with about 600 still in custody.