Sri Lanka, June 4 -- Around 20,000 people are being evacuated from their homes in the German city of Cologne as experts try to defuse three Second World War bombs.

It's the biggest ever post-war evacuation in the city and follows the discovery of two 1,000kg and one 500kg American devices on Monday.

The size of the bombs means that a 1,000m danger zone has to be cordoned off and closed.

Starting from 8am on Wednesday, officials will go door-to-door to check that businesses and houses in Cologne's Old Town and Deutz areas are empty.

Nine schools, 58 hotels, a hospital, the main city hall and the area close to Cologne's famous UNESCO-listed cathedral are among the numerous places temporarily off limits.

Two shelters have been set up fo...