WASHINGTON — (CNN) France launched its first airstrikes from an aircraft carrier against ISIS on Monday as French President Francois Hollande prepared to meet with world leaders in an attempt to build an anti-ISIS coalition.

In Belgium, authorities charged a suspect arrested on Sunday night with participating in activities of a terrorist group in connection with the attack in Paris, Belgium’s Federal Prosecutor Office said Monday. The Belgium prosecutor’s office also said 15 people who were detained have been released

French warplanes took off from the aircraft carrier Charles De Gaulle, which was deployed recently in the eastern Mediterranean, and attacked ISIS targets in Syria and Iraq, said the spokesman for the Etat Major des Armées, the French Chief of Defense Staff.

With the addition of those carrier-based aircraft, France now has 38 aircraft carrying out bombing raids against ISIS, CNN correspondent Jim Bittermann said. France had already been attacking ISIS by air, but not from its carrier.

The French President prepared a diplomatic initiative to form a multi-national force to fight ISIS, the terrorist group that claimed responsibility for the November 13 attacks that left 130 dead in Paris.

Hollande will visit Washington to meet with U.S. President Barack Obama on Tuesday, then meet with German Chancellor Angela Merkel on Wednesday and travel to Moscow to meet with Russian President Vladimir Putin on Thursday.

Hollande met with British Prime Minister David Cameron earlier Monday and they agreed to a pan-European effort for stronger external EU border controls, a more effective way of screening people and greater information sharing, Cameron said.

They also paid their respects to victims of the attacks at the Bataclan concert hall as they visited the site of the deadliest massacre on November 13.

Cameron will make a case for the United Kingdom to start bombing ISIS positions in Syria on Thursday, he said Monday as he presented the country’s defense spending review in Parliament.

He made reference to the attacks in Paris once, when he revealed that the UK has 10,000 military personnel on standby to assist police and emergency services in the event of a terrorist attack.

Russia may be showing signs of warming up to a coalition with France. The Russian Defense Ministry released photos on Monday that showed the words “For Paris” written on Russian missiles that will target ISIS positions.

Report: Third terrorist registered as refugee

An area in the Paris suburb of Montrouge was sealed off Monday night after the discovery in a garbage can of an article resembling a suicide vest, Paris police told CNN.

Investigators were trying to determine whether the article contained explosives. A bomb disposal team on site removed the article.

The German publication Der Spiegel reported Monday that a third suspect in the Paris attacks may have entered France as a refugee.

According to the publication’s online report, investigators recently discovered the third terrorist had been registered as a refugee on the Greek island of Leros. Based on fingerprints and a Serbian passport, the investigators had determined that two men who blew themselves up near the Stade de France had also been registered as refugees there, Der Spiegel said.

Brussels remained under partial lockdown Monday after police carried out raids around the Belgian capital amid warnings of possible terrorist attacks similar to those that killed 130 people in Paris 10 days ago.

Five more people were arrested Sunday night, bringing to 21 the number of people arrested in raids across Brussels and in Charleroi, another Belgian city, said federal prosecutor Eric Van der Sypt.

But authorities found no firearms or explosives in the raids, suggesting they hadn’t defused the threat that has prompted the government to raise the terrorism alert to its highest level for Brussels.

The operation also didn’t uncover Salah Abdeslam, a key suspect in the November 13 attacks on Paris who fled to Belgium in the aftermath and remains on the loose.

CNN security analyst Paul Cruickshank said there’s “unprecedented concern” among Belgium authorities.

“The worry is that there’s another attack team out there, that they have explosives, that they have weapons,” he said Monday morning on CNN’s “New Day.” “Belgian police don’t have a handle on where these guys are and that’s why they’re shaking the tree so hard.”

As the work week begins in Brussels — a major European capital — schools, shopping malls and the subway remain closed. Soldiers and heavily armed police were out in force on the streets, and people were warned to avoid large gatherings. The U.S. Embassy announced that its consular section would close Tuesday because of the high threat level.

“This is a very exceptional situation that I have never seen in my life,” said Alain Destexhe, a 57-year-old member of the Brussels regional parliament. He described the atmosphere in Brussels as “very heavy.”

‘Serious and imminent threat’

Officials haven’t detailed the “serious and imminent threat” announced late Friday, looming over a city that draws millions of visitors every year and houses key European Union institutions.

“We are talking of a threat of several individuals with weapons and explosives, to launch acts, maybe even in several places at once,” Belgian Prime Minister Charles Michel said Saturday, a description with chilling echoes of the Paris attacks the week before.

Michel said Sunday evening that the terrorism alert level for Brussels would stay at 4, the highest level, going into Monday. The alert level for the rest of the nation remains unchanged at 3.

Brussels link to Paris attacks

The tensions in Brussels highlight the city’s strong connection to the Paris attacks, in which ISIS jihadists armed with assault rifles and suicide vests targeted restaurants, a rock concert and a sports stadium.

Several of the men believed to have taken part in the attacks have strong ties to Brussels, notably its suburb of Molenbeek, which has a history of links with terrorism plots.

Abdeslam, who’s on the run, and his brother, who blew himself up at a Paris cafe during the deadly rampage, both hailed from Molenbeek. So did Abdelhamid Abaaoud, the suspected ringleader of the attacks, who authorities say was killed in a police raid near Paris on Wednesday.

French authorities have said the Paris attacks were organized in Belgium, with the jihadists taking advantage of intelligence gaps and the absence of border controls between the two countries to slip into France undetected.

Leaders pay respects at site of massacre

Security measures remain tight in France, which has been under a state of emergency since the attacks.

Children across the country had their bags searched at the front doors of their schools Monday, while administrators were tasked with verifying the identities of everyone on school grounds, according to the Ministry of National Education website.

Police have carried out about 300 searches in the Paris region since the November 13 attacks and about 800 nationwide, the Paris police prefecture spokesman said. As many as 10,000 police officers and 6,500 soldiers are deployed across the capital and its suburbs, he added.

Paris police also announced that a ban on demonstrations has been extended through the end of the month. Despite the ban, several hundred people held a demonstration in Paris over the weekend, with the identities of 58 people forwarded to the Paris prosecutor, police said in a statement.

Did Paris suspect abort part of attack?

Investigators are still trying to establish who did what during the wave of violence across the French capital.

Questions have been raised about whether Abdeslam, 26, might have aborted part of the plan and laid low before calling acquaintances in Brussels to come pick him up.

Another of his brothers, Mohamed, who wasn’t involved in the violence, said he believes Salah Abdeslam might have changed his mind at the last minute and decided not to go through with an attack.

“He probably saw or heard something that was not what he was expecting and he decided not to go through with what he wanted to do,” Mohamed Abdeslam told Belgian broadcaster RTBF.

He reiterated a plea on behalf of his family for his brother to turn himself in.

“We prefer to see Salah in prison than in a cemetery,” he said.

Puzzle over bombers’ identities

French authorities are also still trying to identify all of the seven attackers who were killed on November 13.

The French National Police posted a picture on its official Twitter account of a man it said was one of the three suicide bombers who detonated their explosive vests outside the Stade de France.

The photo is accompanied by an appeal to the public for information about the man, whom officials do not name.

They are also seeking information on another of the stadium bombers, who was found with a Syrian passport that’s believed to be fake or doctored.

In another puzzle, investigators are analyzing the DNA of a third person who was killed during the major police raid Wednesday in the Paris suburb of Saint-Denis that targeted Abaaoud, the suspected ringleader.

Authorities have so far identified Abaaoud and his female cousin, Hasna Ait Boulahcen, as two of the dead in the clash with police. The DNA of the third person, who is believed to have detonated a suicide device, doesn’t match anyone on police records, according to CNN affiliate BFMTV.

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