Belgian armed police mounted raids across the country late on Sunday after the prime minister announced another day of lockdown in the capital for fear a new, Paris-style mass attack may be imminent.

Shortly before midnight, the public broadcaster, announcing several arrests, said the operations had concluded. Prosecutors plan a news conference at 00:30 a.m. (2330 GMT).

Earlier in the evening, Prime Minister Charles Michel, speaking after a meeting of security chiefs called to review the threat status, said the capital's metro, universities and schools would be closed on Monday.

For the rest of the country, a threat level of three on a four-tier scale would remain in place, Michel said. Brussels would remain at level four, meaning an attack was imminent, as it has been since Saturday.

"What we fear is an attack similar to the one in Paris, with several individuals who could possibly launch several attacks at the same time in multiple locations," Michel told a news conference.

Armed police mounted searches in several parts of the capital on Sunday evening and cordoned off areas close to the  main tourist attraction, the Renaissance Grand Place around the town hall. The public broadcaster said there were also raids near Liege in the east and Charleroi, south of Brussels.

Helicopters could be heard flying over the capital.

Possible targets were malls, shopping streets and public transport, Michel said, adding the government would boost police and army presence in the capital beyond already high levels.

He said a new evaluation of the situation would be made on Monday afternoon and everything was being done to return the city to normal as quickly as possible.

Commuters trying to get to work on Monday are expected to suffer delays as a result of the metro closure, though some companies had already indicated on Sunday they were ready for staff to work from home.

Belgium has been at the heart of investigations into the Paris attacks on Nov. 13 that left 130 people dead after links with Brussels emerged.

UPDATE: Belgian police arrest 16, fail to find Paris attacks key suspect

In France, investigators on Sunday extended into a fifth day the detention of a man arrested on Wednesday outside the building where the suspected ringleader of the Paris attacks died in a raid. Police also released a picture of a man they said had blown himself up in the attacks and called for witnesses.

Two of the Paris suicide bombers, Brahim Abdeslam and Bilal Hadfi, had been living in Belgium. Fugitive suspected militant Salah Abdeslam, Brahim's 26-year-old brother, slipped back home to Brussels from Paris shortly after the attacks.

Earlier, Interior Minister Jan Jambon said Salah Abdeslam was not the only security threat.

"It is a threat that goes beyond just that one person," he told broadcaster VRT. "We're looking at more things, that's why we've put in place such a concentration of resources."

Bernard Clerfayt, the mayor of the Brussels district of Schaerbeek, was quoted by broadcaster RTBF as saying there were "two terrorists" in the Brussels area ready to carry out violence.

Mohamed Abdeslam, the brother of Brahim and Salah, urged Salah in an interview on RTBF television to give himself up, adding that he believed Salah was still alive because he had had a last-minute change of heart while in Paris.

WITHOUT PRECEDENT SINCE WORLD WAR TWO

Intelligence, police and judicial officials reviewed the alert status during the day. The national security council, including top ministers, convened later on Sunday.

The government has advised the public to be alert rather than panic-stricken. People have been told to avoid crowds in the capital, while authorities have also closed museums, cinemas and shopping centres. Clubs and venues have cancelled events.

Brussels' chief rabbi Albert Gigi told Israel's Army Radio on Sunday that the city's synagogues were shut over the weekend for the first time since World War Two.

Soldiers are on guard in parts of Brussels, a city of 1.2 million people and home to institutions of the European Union and the headquarters of NATO.

That said, Brussels on Sunday morning resembled most other Sundays, with the normal limited number of shops, such bakeries and small supermarkets open, and many churches in the largely Catholic country still holding services. However, larger markets were shut.

The latest measures go far beyond those taken the last time Brussels was put on level four alert, for about a month at the end of 2007 and the start of 2008, when authorities intercepted a plot to free convicted Tunisian Nizar Trabelsi from a Belgian jail.

Then the city closed the downtown Christmas market early and cancelled its New Year fireworks display.

(Additional reporting by Robert-Jan Bartunek and Robin Emmott in Brussels; Editing by Ros Russell, Giles Elgood and Alastair Macdonald)

UPDATE: Belgian police arrest 16, fail to find Paris attacks key suspect

Latest news

Syrian opposition rules out future role for President al-Assad

The Syrian opposition said Friday it would not accept any role for President Bashar al-Assad in the future of the war-torn country, reacting to a recent US shift saying that removing al-Assad is no longer a priority for Washington.

Russian Army integrates breakaway forces of Georgian province

Parts of the small fighting forces of the Georgian breakaway province of South Ossetia have been placed under Russian military control, Russian Defence Minister Sergei Shoigu said on Friday.

Czech Republic's Pilsner Urquell beer is now Japanese

Japanese brewing company Asahi completed its takeover of the Czech brewery Pilsner Urquell on Friday, Asahi said in a statement.

Judge approves 25-million-dollar settlement of Trump University case

A US district judge on Friday approved a 25-million-dollar settlement of lawsuits and state fraud allegations against Trump University, the US president's now-defunct business venture.

Former Thai premier Thaksin to junta on reconciliation: 'Cut me out'

Former Thai prime minister Thaksin Shinawatra on Friday announced that he is not interested in the junta-led reconciliation process, three days after the junta handed him a half-a-billion-dollar tax bill for his past business deal.

Dalic: We welcome possible deal between Agrokor and banks

The government welcomes the possibility of an agreement being concluded between the Agrokor food company and creditor banks, and the bill on vitally important companies is not a fallback plan but the result of the government's care for the overall economic and financial stability of Croatia, Deputy Prime Minister and Minister of Economy Martina Dalic told a press conference in Zagreb on Friday.

Croatia, China sign action plan for cooperation in agriculture

The Croatian and Chinese ministries of agriculture on Friday signed an action plan for cooperation in the field of agriculture for the period 2017-2018, the Croatian ministry said in a statement.

ZSE indices up, Agrokor shares in focus of investor interest

The Zagreb Stock Exchange (ZSE) indices on Friday rose by more than 1.8%, with stocks of the Agrokor food and retail concern being in the focus of investor interest again.

Berlin police defend handling of Berlin market attacker

Berlin police defended themselves on Friday against accusations that they stopped surveillance on Berlin Christmas market attacker despite knowing in June 2016 he was dangerous.

Croatia, creditors tailor emergency measures to save tottering giant

Croatia's tottering retail and food giant Agrokor reached an agreement with its creditors, putting its debts standby and allowing it to continue working during emergency restructuring, the Croatian branch of Austria's Erste Bank said Friday.

Agrokor's creditors say standstill agreement to go into force today

A standstill agreement regarding the Agrokor concern's existing financial obligations to banks will take effect on Friday, additional capital will be injected into the concern in the coming days and the concern will be actively restructured, which includes a change of its management, it was said on Friday after a meeting between Agrokor's suppliers and creditor banks.

Palestinians, UN slam Israel's new settlement plan

Palestinians, Israeli activists and the UN lambasted the government of Israeli Prime Minister Benjamin Netanyahu on Friday, a day after it gave the go-ahead for the first new West Bank settlement in a quarter of a century.

South Sudan rebels release three abducted foreign oil workers

South Sudanese rebels have released three foreign engineers they abducted in early March in the oil-rich Upper Nile region, Foreign Affairs Ministry official Mawein Makol Arik said on Friday.

Turkish opposition: Imprisoned party chief has gone on hunger strike

The head of Turkey's pro-Kurdish opposition party has launched a hunger strike from prison.

European leagues threaten Champions League schedule clashes

The European Professional Football Leagues (EPFL) on Friday threatened schedule clashes on Champions League matchdays in an ongoing dispute with the governing body UEFA.

Danish court revokes citizenship of IS volunteer

A Danish appellate court on Friday stripped a man of his Danish citizenship for volunteering to fight for the extremist Islamic State in Syria.

Banks and Agrokor agree on key elements of standstill agreement

Member banks of the coordinating committee of financial creditors and representatives of the Agrokor food company have in principle agreed on key elements of a standstill agreement, which is expected to be signed later today, announcing changes in the company's management team, Erste Bank said in a statement on Friday afternoon.

Syrian man on trial in Sweden; mosque attack labelled terrorism

A Syrian man went on trial Friday in the southern Swedish city of Malmo, charged with terrorism and arson after an attack last year on a building used as an assembly hall by Shiite Muslims.