Berlin  - A lost Russian bomb from the Second World War was discovered Friday just outside the Berlin apartment of Chancellor Angela Merkel, triggering a city-centre lockdown as bomb-disposal experts set about defusing it.

The 100-kilogram bomb was discovered just 10 centimetres below the sandy surface of a museum forecourt.

Merkel lives on the Island of Museums, between two arms of the Spree River. The bomb was found in front of the Neues Museum, one of five museums of art and antiquities which have given the central-city island its name.

While bomb experts worked on the device, a railtrack carrying express and suburban trains was closed and streets were blocked.

Sources said that before they began, Merkel arrived in the cordoned-off area in her chauffeured limousine with her police bodyguards and quickly fetched something from the apartment before driving away again in her motorcade.

Unexploded bombs dropped by the Second World War allies are frequently found in German cities. (dpa)