Belgian authorities have announced charges against a fourth suspect on terrorism charges related to the terrorist attacks in Paris.
The Federal Prosecutor's Office said on November 23 that the man, who was not identified, was detained in a series of police raids in Belgium late on the previous day.
Another 15 people arrested in the raids were released after being questioned.
The statement said the man had been charged with "participating in activities of a terrorist group and with [a] terrorist attack."
Of five people detained earlier on November 23, two have been released while "further enquiries" are under way regarding the others, the prosecutor's office said.
The November 13 coordinated assaults in Paris, claimed by Islamic State (IS) militants, left 130 people dead.
Belgium had already charged Mohammed Amri and Hamza Attou with aiding fugitive Salah Abdeslam, who is suspected of participating in the Paris attacks.
Abdeslam, 26, a Brussels barkeeper whose elder brother blew himself up during the Paris attacks, has been the focus of a manhunt by French and Belgian authorities.
A third, unnamed suspect had also been charged.
Also on November 23, Belgium's Prime Minister Charles Michel said the terrorism threat level for the Belgian capital, Brussels, was being maintained at the maximum level, warning of an imminent threat.
However, he said schools and the subway in the city will progressively reopen, starting on November 25.
For the rest of the country, a threat level of three on a four-tier scale will stay in place.
The Belgian capital's metro network was closed during the weekend and major events like soccer matches were cancelled.
Extra security has been deployed on trains, in railway stations, and at airports.
The mayor of Brussels has also ordered restaurants and cafes across the city to close, along with shopping centers and public buildings.
Brussels has been at the center of investigations into the Paris attacks since it emerged that several of the attackers had been living in the country, including Abdelhamid Abaaoud, the man who authorities say orchestrated the plot. He was killed last week in a standoff with French police.
In a separate development, French police sources said a "belt that may resemble an explosive belt" was found on November 23 in a dustbin in the southern Paris suburb of Montrouge.
Officials said the vest, which did not have a detonator, was found by a streetcleaner in a pile of rubble in Chatillon-Montrouge, just south of Paris, on November 23.
The Associated Press cited a French police official as saying that laboratory analysis determined that the explosive material on the vest was the same as that used in seven similar vests used in the Paris attacks, which Islamic State (IS) militants have claimed responsibility for.
Sources close to the investigation said the vest had a similar "configuration" to those used in the Paris attacks and that telephone data places Salah Abdeslam, in the same area on the night of the bomb and gun attacks.
An unidentified source quoted by Reuters said that it was too soon to say whether Abdeslam had come into contact with the vest.
In the French capital, Britain's Prime Minister David Cameron accompanied French President Francois Hollande in a visit to Paris's Bataclan concert hall, where 90 people died in the bloodiest of the multiple attacks.
Cameron said he would ask for parliamentary approval for the United Kingdom to join air strikes against IS extremists in Syria.
Hollande vowed to continue strikes against the IS group in Syria and Iraq, saying, "We will intensify our strikes, choosing targets that will do the most damage possible to this army of terrorists."
France, meanwhile, launched its first combat missions against IS militants from its Charles de Gaulle aircraft carrier, which was deployed to the Mediterranean Sea in the wake of the deadly attacks in the French capital.
The Defense Ministry said the strikes had hit IS targets in the Iraqi cities of Ramadi and Mosul, as well as in Raqa, the main stronghold of IS militants in Syria.
The nuclear-powered aircraft carrier has 26 fighter aircraft, tripling France's capacity to carry out strikes.
It is accompanied by two French frigates, a supply ship, and a submarine, as well as a Belgian frigate and a British destroyer.
With reporting by AFP, dpa, AP, and Reuters