Army chief of staff Nikos Phanios said the bomb’s firing mechanism “was still in a very good shape, and this was what had us worried.” The device was American-made he said.

According to Greek media reports, the bomb was dropped by a British plane during air strikes on the city’s nearby railway station and port in 1943 in which hundreds of local inhabitants died.

The start of the operation was slightly delayed as police removed a camera that had been placed above the crater by a Greek media outlet in breach of guidelines for covering the event.

Some 70,000 people were evacuated within a 1.9km radius of the site, affecting three working-class neighbourhoods west of the city centre.

The operation was unprecedented in Greece, “where a bomb of this size has never been found in an area this densely populated,” Tzitzikostas said. He praised the population for its discipline.

But shopkeeper Stelios Orphanos said many chose to stay at home, “because they are scared of thieves.”

Most of the buses brought for evacuation remained empty as many people left on their own. Some 400 refugees in a nearby camp were also bussed to safer areas.

Seven decades after the end of the second world war, unexploded bombs from the conflict are still being found around the globe.

On January 23, dozens of people were evacuated after a bomb was found near a Hong Kong university, while three days before that Britain’s navy disposed of a suspected wartime bomb found close to the parliament in London.

In the German city of Augsburg, 54,000 people had an unwelcome Christmas surprise on December 25 when they had to leave their homes while authorities dealt with a bomb dropped by Britain during the war.