MORE than 20,000 residents were being evacuated from central Cologne today as experts prepared to defuse three unexploded US bombs dating back to World War II.

The bombs were discovered on Monday during preparatory roadworks in the city’s Deutz district, just across the Rhine from Cologne’s historic centre.

Despite the war ending over 80 years ago, unexploded ordnance from Allied air raids is still regularly unearthed across Germany. 

Large-scale evacuations are common, but this marked Cologne’s biggest since 1945.

Authorities began moving about 20,500 people out of a 3,280-foot radius around the bomb site early this morning. 

The evacuation zone included 58 hotels, nine schools, several museums, office buildings and the Messe/Deutz railway station.

Three bridges across the Rhine were also within the zone, including the Hohenzollern railway bridge, one of the country’s busiest, which was shut down during the operation. 

Shipping on the Rhine was suspended as a precaution.

Officials warned residents that failure to comply with evacuation orders could result in heavy fines. 

”If you refuse, we will escort you from your home — if necessary by force — with the police,” authorities said.

Patients, including those in intensive care, were transported from the Eduardus Hospital by ambulance.

Authorities said that the operation to defuse the bombs would continue throughout the day and was dependent on confirming the area had been fully cleared.

It is expected that about 1.5 million bombs were dropped on Cologne during the war, with about 20 per cent not fully detonating.