Receding Rhine reveals large unexploded WW2 bomb

German explosives experts were on Thursday preparing to defuse a large World War II bomb found near Cologne after exceptionally low water levels on the Rhine river exposed the device.

Around 360 people living or working within a 400-metre radius of the site were due to be evacuated, city officials said. Those affected include residents of a retirement home and staff at the nearby RTL television studios.

The 500-kilogram US aerial bomb was discovered on Wednesday evening near Cologne's Rheinpark. The exact time of the defusing operation has not yet been announced.

The discovery came as the Rhine again reached a record low water level in Cologne after prolonged heat and drought. The gauge fell to 67 centimetres on Thursday, matching the historic low recorded just days earlier, with a further drop to 66 centimetres forecast later in the day.

Low water levels have disrupted shipping along Germany's busiest inland waterway, forcing vessels to carry reduced loads, while exposing objects long hidden beneath the river. Officials said water levels were expected to rise only slightly in the coming days, with no sustained recovery in sight.