Berlin’s biggest railway station, government ministries and a hospital are to be evacuated on Friday after the discovery of an unexploded second world war bomb, police have said.

Buildings and streets in a radius of 800 metres around the site north of the busy train station would be cleared from 9am until the 500kg (1,100-pound) explosive was safely defused, they said on Wednesday.

The evacuation zone covers the central railway station, the economy and transport ministries, an army hospital and the embassies of Indonesia and Uzbekistan, according to a police spokesman.

Police said it was not yet clear how many thousands of people would be affected but predicted on local media that “it will be big, it will be a major hassle”.

The Deutsche Bahn rail company and urban transport operators prepared for large-scale disruptions around the central hub for trains, trams and buses.

The bomb, which was discovered during construction work on Heidestrasse in the district of Mitte, was “safe for now”, police said, reassuring nearby residents that “there is no immediate danger”.

Allied planes extensively bombed Nazi Germany during the second world war, and vast urban and industrial areas remain littered with unexploded devices and other ordnance often found during construction projects.

Last Friday, in the state of Bavaria, an ordnance disposal team defused a 500kg bomb that had forced the evacuation of 12,000 people in the city of Neu-Ulm – the third unexploded bomb to be disarmed in recent weeks in the city of 50,000 people.