Europe's worst drought in years has pushed the mighty river Danube to one of its lowest levels in almost a century, exposing the hulks of dozens of explosives-laden German warships sunk during World War Two near Serbia's river port town of Prahovo.

Hungary, which has had success in resolving water-management issues with its neighbours in eastern and central Europe that share the Danube River, has been asked to help Thailand work out a plan for the Mekong.