More than 75 years after it plunged from the sky above Frankfurt, a US-made bomb has driven a fresh generation of Germans to flee their homes and take shelter.

The 500-kilogram blockbuster, discovered during construction works, is set to be defused after days of planning, while thousands of residents coped with the emergency evacuation.

Authorities have created an exclusion zone around the area, which includes the site of the European Central Bank and multiple hospitals and care facilities. The Frankfurt Zoo will also be closed .

About 16,500 people will have to leave their homes before 8am.

Once police have ensured that nobody is in the area, experts will begin defusing the bomb in what is expected to be a six-hour operation.

A blockbuster bomb bound for Germany is loaded into the belly of a bomber during WWII.  Photo: WWII Data Base

Frankfurt’s fire services are well-versed in bomb disposal operations. In September 2017, 65,000 residents had to be evacuated so that a British “blockbuster” bomb weighing 1.8 tonnes could be removed.

The bomb disposal will also impact transport in the city as roads in the area will be closed and trains and buses forced to re-route or end their journey at certain stops.

German authorities estimate that around 15 per cent of the bombs dropped during WWII failed to explode, and more than 2000 tons of unexploded weaponry are found each year.

In the rush to rebuild after the war, Germans often just buried the munitions.