Thousands of people were evacuated from a central area of the German capital Berlin and police shut down the main train station as a precaution while experts defused and removed an unexploded World War II bomb found during recent construction work.

Some 10,000 residents and workers were forced to leave the two square kilometre area while bomb experts defused the 500-kilogram British bomb dropped during the war.

Berlin's main train station was closed as a precaution. ( AP: Michael Sohn )

Trains were prevented from stopping at the busy station from 10:00am, and through traffic was shut down at 11:30am before experts began their work, German rail operator Deutsche Bahn said.

Some 300,000 travellers use the station daily.

Bomb disposal experts were able to successfully remove the detonator just after 1pm and destroy it in a small controlled explosion.

The unexploded 500 kilogram bomb was found at a construction site. ( AP: dpa )

The evacuation area, a circle around the construction site north of the train station where the bomb was discovered during digging, also included a hospital, the new offices of Germany's foreign intelligence service, and parts of both the economy and transportation ministries.

Chancellor Angela Merkel's office and Germany's parliament building are close by, but outside the zone.

Experts say more than 5 per cent of the bombs dropped on Berlin failed to explode. ( AP: Britta Pedersen )

Even 73 years after the end of the war, such discoveries remain common in major German cities.

Downtown Berlin was largely reduced to rubble in hundreds of Allied bombing raids during the war and street-to-street fighting between the Nazi and Soviet armies in the final days of the conflict.

It's estimated that more than 5 per cent of the bombs dropped on Berlin failed to explode due to a variety of reasons, including faulty fuses, poor assembly and bad angle of impact.

The city estimates at least 3,000 bombs, grenades and other munitions are still buried.

ABC/Wires