Belgian authorities say 16 people have been arrested in the Brussels region during police raids linked to their investigation of the November 13 Paris terrorist attacks.
Eric Van Der Sypt, a spokesman for Belgium’s federal prosecutor, said early on November 23 that a key suspect in the case, French-born militant Salah Abdeslam, was "not among those arrested during the searches."
Belgian officials would not release details about the identities of those detained, nor specific charges against the suspects, "in the interest of the investigation" while security operations are continuing.
In Paris, British Prime Minister David Cameron accompanied French President Francois Hollande on a visit to the Bataclan concert hall, where 90 people died in the bloodiest of the Paris terrorist attacks.
Cameron said he will ask for Parliamentary approval for the United Kingdom to join air strikes against Islamic State extremists in Syria.
The late-night raids on November 22 included 19 house searches in the Brussels region as well as three house searches in Charleroi, a city in southern Belgium's Wallonia region.
Officials said they did not find any guns or explosives during the searches.
However, Van Der Sypt said that during a search of a snack bar in the Sint-Jans-Molenbeek district of Brussels, a driver rammed his vehicle "into the police" and sped off.
He said police fired two shots at the fleeing vehicle, and that the driver -- "a man who was hurt" -- was "intercepted later in Brussels" and placed under arrest.
Van Der Sypt said, "For the time being, we cannot confirm if there is a relation between the ongoing investigation and this arrest."
Brussels remains on its highest alert level as a result of what Belgium's prime minister has called a "serious and imminent" threat of coordinated, multiple attacks by Islamist extremists.
The Level 4 security alert for Brussels was declared on November 21.
Earlier media reports suggested the heightened terror threat was linked to concerns Abdeslam, a 26-year-old who is thought to be one of the ringleaders of the Paris attacks, was hiding in the Brussels area.
But Interior Minister Jan Jambon said on November 22 that the current threat was greater than that posed by Abdeslam.
"It is a threat that goes beyond just that one person," Jambon told Flemish broadcaster VRT. "We're looking at more things. That's why we've put in place such a concentration of resources."
Prime Minister Charles Michel told reporters in Brussels on November 22, "What we fear is an attack similar to the one in Paris, with several individuals who could also possibly launch several attacks at the same time in multiple locations."
He said possible targets were commercial centers, shopping streets, or public transport.
The city's subway system will stay closed and all schools and universities will be shut on November 23, Michel said following a meeting of the national security council to review the situation in the country.
For the rest of the country, a threat level of three on a four-tier scale would stay in place, Michel said.
He said a new evaluation of the situation would be made on November 23 in the afternoon while adding that and everything was being done to return the city to normal as quickly as possible.
The Belgian capital's subway network was closed during the weekend and major events like soccer matches were canceled.
Extra security has been deployed on trains, in railway stations, and at airports.
The mayor of Brussels also has ordered restaurants and cafes across the city to close, along with shopping centers and public buildings.
Islamic State militants claimed responsibility for the Paris attacks that killed 130 people.
Brussels has been at the center of investigations since it emerged that two Paris suicide bombers had been living in Belgium.
Another alleged ringleader of the Paris attacks, 28-year-old Abdelhamid Abaaoud, was a Belgian of Moroccan origin.
He was killed during a raid by French security forces in a Paris suburb on November 18.
Belgian police staged nine raids on November 19 and arrested nine suspects who are accused of being linked to the Paris terrorist attacks.
Many of those raids were conducted in the largely immigrant area of Molenbeek, where Abaaoud is from and where Salah Abdeslam and his brother, Brahim, previously resided.
Belgium also has filed criminal charges against three of its citizens who were detained in Paris in connection with the attacks.
Brussels police said they discovered a laboratory for the production of explosives during a raid in the capital on November 21.
Weapons were also discovered at the site, but no explosives or suicide belts were found.
Police added that three people were detained in that raid, but did not provide details.
Officials around the world are investigating the mostly French and Belgian network thought to have carried out the Paris attacks with help from Islamist extremists in Syria.
On November 21, police in Turkey detained three suspected terrorists -- including a Belgian citizen, Moroccan-born Ahmet Dahmani, who is suspected of having scouted out locations for the Paris attacks as part of the planning.
Brussels, a city of more than 1 million people, hosts the headquarters of the European Union and NATO, as well as many large corporations.