Belgium has reduced the terror alert in Brussels, five days after it was raised to the highest possible level that saw schools and the metro closed, the government’s crisis centre says.

“We can confirm that the Threat Analysis Coordination Agency re-evaluated the threat level from four to level three,” a spokesman for the crisis centre, which is part of the interior ministry, told AFP.

Belgian Prime Minister Charles Michel said the threat of an attack in the city remained serious but was not as imminent as it had been.

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“The situation is serious, but according to the indications of the security services, it is not as imminent as previously assessed,” Mr Michel said.

There were no immediate details on what basis the agency reduced the threat level, with the national security council of top government officials set to decide on the consequences at a meeting later on Thursday.

The alert level was raised early on Saturday after the government warned of a “serious and imminent threat” of attacks in the capital similar to the Paris atrocities that left 130 people dead on November 13.

The city was locked down with armed police and troops patrolling near deserted streets and the metro system completely shut down, while schools stayed shut on Monday and Tuesday.

Schools and the metro system reopened partially on Wednesday despite two suspects from the Paris attacks still being at large.

Brussels mosque alert powder turns out to be flour

On Thursday, Belgian emergency services evacuated the biggest mosque in Brussels and decontaminated 11 people after the discovery of a suspicious package containing what turned out to be flour.

Firefighters in chemical suits and gas masks were called in to the Great Mosque of Brussels amid fears that white powder in the package could be anthrax.

“It was just flour. Everything is negative, the cordon has been lifted,” Brussels fire brigade spokesman Pierre Meys told AFP after the mosque was sealed off for three hours, adding that the substance had been analysed at a laboratory.

The mosque, the city’s biggest, is located just a few blocks from the major EU institutions and many embassies and was cordoned off by police and firemen.

Fire brigade captain Anne Wibin, who was at the scene, said 11 people, including two police officers, were decontaminated as a precautionary measure after the package was found.

“A parcel was found at the entrance to the mosque and found to contain white powder. We are taking all preventative measures in case it is anthrax but it is a precautionary measure,” she said earlier.

“People in direct contact were isolated and decontaminated and also those who were in indirect contact.”

The Great Mosque, given as gift by Belgium to Saudi Arabia in 1967 which then carried out reconstruction work, sits on a corner of Cinquantenaire Park where many of the thousands of EU staff take a lunchtime break and families bring their children to play.

It is no more than 200 metres from the top EU institutions — the European Council and the European Commission — plus other offices and many embassies.