Brussels fears 'gun and explosives' attack

He urged the public “not to give in to panic, to stay calm,” adding: “We have taken the necessary measures.”

He spoke after Belgian authorities, at 5am on Saturday, raised the terrorist alert level from three to four - the maximum, indicating a “serious and imminent” threat.

They deployed military patrols, including armoured vehicles, in the city centre and urged people to avoid public places.

Main shopping streets were almost empty at noon.

Metros and some trams stopped running. Trains reduced services and parking restrictions were imposed at the Belgian national airport.

Some tourist attractions, such as the Atomium, closed.

Shopping malls, large cinemas, and libraries closed.

Marc Filipson, the owner of the Filigranes bookshop chain, also closed, said in a statement: “Ideologically speaking, I feel like crying.”

Rock star Johnny Hallyday cancelled his performance at the Heysel venue. The Ancienne Belgique concert hall put off its Sound/Check event.

The Belgian soccer league initially ignored warnings, but later cancelled matches.

Foreign minister Didier Reynders, earlier on Saturday, noted: “When there's a search on, it's easier for the police if there aren't too many people walking around on the streets.”

Rudi Vervoort, the Brussels City mayor, told people to stay “vigilant."

He said bars and restaurants haven't been advised to close. Christian masses and other religious events are also to take place.

For their part, EU institutions disseminated the Belgian alert to staff by email.

Kristalina Georgieva, an EU commissioner, tweeted: "Please stay safe and follow advice of public authorities."

The British foreign office said: "Attacks could be indiscriminate, including on public transport and transport hubs and in places frequented by foreigners."

"Brussels hosts a number of international institutions (EU and Nato) and government and foreign embassy buildings which are sensitive locations."

The US embassy in Brussels urged “everyone to shelter in place and remain at home. If you must go out, avoid large crowds."

The US military ordered its Brussels-based personnel, including civilian staff, and their families to stay home.

Paris links

The alert comes after Belgian police, on Friday, found weapons in a raid in Molenbeek - a poor district in Brussels with a high Muslim concentration, said to have been frequented by some of the attackers involved in last week’s Paris atrocity.

Police said it found guns, but not explosives.

One of the Paris attackers, Salah Abdeslam, is at large and believed to be in northern Europe.

Turkish authorities, on Saturday, also detained a Belgian national of Moroccan origin, 26-year old Ahmad Dahmani, said to have links to the Paris murders.

Brussels was last time on maximum alert in 2014 during a shooting at the Jewish Museum in the Place Sablon area.