A prolonged drought which has caused rivers in Poland to reach record low levels has led to the discovery of important Second World War artefacts - including a Soviet fighter plane and several Jewish tombstones.

The Vistula River, which flows 651 miles through Poland from the Beskidy Mountains to the Baltic Sea, is now at its lowest level since measurements started in the late 18th century and has recently unveiled a number of treasures. The discoveries were made just days after stone fragments from the early 20th-century Poniatowski Bridge - which crossed the Vistula River in Warsaw, and which the Germans blew up in 1944 as they crushed the Warsaw Uprising - were found. The bridge was then rebuilt after the war.

Officials have known for years that archaeological treasures are hidden under the murky waters of the Vistula River and its tributaries but until now it has been impossible to carry out searches. On Sunday an archaeological group found the remnants of a Soviet fighter bomber in the Bzura River, a Vistula tributary, near the village of Kamion in central Poland.

The pieces have now been moved to a museum in nearby Wyszogrod for examination and the group intend to carry out more recovery work on Saturday. Parts of Soviet uniforms, a parachute, a sheepskin coat collar, parts of boots, a pilot's TT pistol and radio equipment were found along with a lot of heavy ammunition. The inscriptions on the control panel and the radio equipment are in Cyrillic. The discoveries all help to paint a picture of Poland between 1939 and 1945 - a German invasion from the west, a Soviet invasion from the east, the murder of Jews across occupied Poland and fighting between the Soviets and Germans after Adolf Hitler turned on former ally Josef Stalin.