AUTHORITIES will keep Brussels on the highest state of alert into the start of the working week because of the “serious and imminent” threat of a Paris-style attack, the Belgian Prime Minister said.

Schools and universities in Brussels will be closed and the city’s underground will remain shut, government officials decided at a meeting yesterday of the country’s National Security Council.

With one suspect in the November 13 attacks in Paris last seen crossing into Belgium, much of Brussels was in lockdown over the weekend.

Officials also recommended that sports competitions and all activities in public buildings be cancelled, and shopping and commercial centres closed.

Belgium’s national crisis centre has raised its terrorism alert for the Brussels region to Level 4, which indicates a “serious and immediate threat”.

Prime Minister Charles Michel said the decision to raise the threat alert to its highest setting was taken “based on quite precise information about the risk of an attack like the one that happened in Paris ... where several individuals with arms and explosives launch actions, perhaps even in several places at the same time”.

Several weapons were discovered during the search of the home of one of three people arrested in connection with the Paris attacks, but said no explosives were found.

Authorities across Europe, the Middle East and the US are trying to determine how a network of primarily French and Belgian attackers with links to Islamic extremists in Syria plotted the deadliest violence in France in decades, leaving 130 people dead.

A new potential link has emerged in Turkey, where authorities said they detained a 26-year-old Belgian suspected of connections to Islamic extremists, and possibly to the Paris attacks.

Reports identified him as Ahmet Dahmani, and said he is suspected of having explored areas of Paris targeted in the attacks.

Brussels was the home of Abdelhamid Abaaoud, the suspected organiser of the Paris attacks, and Belgium has filed charges of “participation in terrorist attacks and participation in the activities of a terrorist organisation” against three other suspects.

At least one Paris attacker, Salah Abdeslam, crossed into Belgium the morning after the attacks but Paris officials say they have no firm information on his whereabouts.

Brussels, a city of more than one million, is home to the headquarters of the European Union, Nato and the offices of several multinational corporations.

Residents were told to avoid gatherings, train stations, airports and commercial districts. Service has been halted on the Metro and underground trams.

Many stores and shopping centres have shut their doors on what would normally be a busy shopping day in the lead-up to Christmas.

The Royal Museums of Fine Arts of Belgium closed for the weekend, and a Saturday evening concert by French rocker Johnny Hallyday was rescheduled.

Concerns about Europe’s porous borders prompted interior and justice ministers meeting in Brussels on Friday to promise tighter controls to make it easier to track the movements of jihadis with European passports travelling to and from Syria.

Two of the seven terrorists who died in the attacks had entered Europe through Greece, an entry point for thousands of migrants seeking asylum in Europe.

The five other attackers who died had links to France and Belgium. One of the seven dead has not been identified, while a manhunt is under way for one suspect who escaped, 26-year-old Abdeslam. French police stopped him the morning after the attacks at the Belgian border but let him go.

His brother Brahim blew himself up in the Paris massacres. The suspected ringleader, Abdelhamid Abaaoud, was killed in a raid on Wednesday in a raid in the Paris suburb of Saint-Denis.

Seven of the eight people detained in that raid have now been released.

Don’t blunder into another conflict, SNP's Stewart Hosie warns David Cameron

Carolyn Leckie: We must not let fear erode our humanity

Belgium: Brussels maintains lockdown over threat of Paris-style terrorist attack

Alyn Smith: We must act to halt rights violations in Bangladesh

Paris attacks ‘mean police cuts must stop’

Scottish Defence League bigots fail to disrupt refugee rally in Glasgow

Letters to The National, November 23: Solidarity is needed in wake of attacks

The National View, November 23: Going to war in Syria seems a certainty, but what will come after the bombing?