Bomb diffusion Greece
Military officers of the Hellenic Army's Explosives Ordnance Disposal (EOD) stand over a hole in the ground where a 250 kg World War Two bomb was found during excavation works at a gas station, before an operation to defuse it, in the northern city of Thessaloniki, Greece, February 12, 2017 REUTERS/Alexandros Avramidis

Around 72,000 people living in Greece's second biggest city Thessaloniki were evacuated on Sunday (12 February) so that military officials could diffuse a 250kg (550lb) unexploded Second World War bomb.

The explosive, which was dropped in the 1940s, was discovered a few days back about 5 metres (16 feet) underground when the expansion was being carried out at a petrol station.

More from IBTimes UK

This is being described as the biggest peacetime evacuation in Greece's history as all those living in the 2km radius of site, were urged to move out of the area.

Police officials told Reuters that buses were arranged to move the residents to local stadiums, cafes and gyms. The ministry of migration said that refugees living in nearby abandoned factories would be also taken on a museum visit in Thessaloniki.

Regional Governor Apostolos Tzitzikostas told a local news channel, "We are absolutely ready. I call on our fellow citizens to stay calm. There is no reason to panic, there is no danger, the measures taken are precautionary and for the safety of residents."

He added that the operation is expected to last "at most six hours". Around 1,000 police officers and 300 volunteers will be deployed for the operation.

An army spokesperson, Colonel Nikos Fanios said that the exterior of the device was too degraded to determine whether it was a German or an allied bomb.

"We don't know what we're going to find... [diffusing it and moving it to a military range] could take us up to two days," he added.