Brussels on high alert as police hunt Paris attack fugitive

Brussel: Brussels will remain on the highest alert level and maintain security measures that have severely disrupted normal life in the city until at least Monday as it faces an "imminent" threat of attack, Belgium's prime minister said today, urging his population to remain calm.

In France, police said an explosive belt had been found in the southern Paris suburb of Montrouge. A police official, who couldn't be named because he wasn't authorised to discuss the investigation, said the belt was found without a detonator by a street cleaner in a pile of rubble today and was being analysed by police.

Belgian Prime Minister Charles Michel said the country's capital, which also houses the headquarters of the European Union and NATO, faced a "serious and imminent" threat of attack, while the rest of the nation would stay at the second-highest level.

The country's crisis center said the alert level would only change this week if a significant breakthrough by investigators warranted it.

The increased security measures in the wake of the November 13 Paris attacks that killed 130 people and wounded hundreds have virtually shut down the city, with the subway and shops closed over the weekend and schools remaining shut on Monday.

Michel said that despite the alert level, schools and the subway system would reopen progressively as of Wednesday.

"We are very alert and call for caution," Michel said. "The potential targets remain the same; shopping centers and shopping streets and public transport."

"We want to return to a normal way of life as quickly as possible."

The unprecedented security measures come as authorities hunt for one or more suspected extremists, including Salah Abdeslam, a fugitive since being named as a suspect in the Paris attacks. He has yet to be found.

Belgian authorities arrested a suspect on terrorism related charges Monday after a series of raids that saw 21 people detained between Sunday night and midday today.

The federal prosecutor said the suspect, who was not identified, was charged with terrorism offences related to the Paris attacks after authorities detained 16 people yesterday.

Three others were charged with similar offenses last week. The other 15 people detained Sunday evening were released.

Earlier in the day, British Prime Minister David Cameron said in Paris that he will ask for parliamentary approval for the UK to join airstrikes against Islamic State extremists in Syria.

If approved, Britain would join other nations carrying out bombings in Syria, including the US, France and Russia.