PARIS (CBSNewYork/AP) — A French man believed directly involved in Friday’s attacks in Paris that killed 129 people in the worst violence in France in decades is on the run and the subject of a manhunt, French security officials said Sunday.

The man, one of three brothers believed involved in the killings in central Paris, rented a black Volkswagen Polo used by a group of hostage-takers that left at least 89 people dead inside the Bataclan concert hall, one official said.

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The manhunt is believed to involve at least one suspect, another official said. Both spoke on condition of anonymity because the investigation is ongoing. One of the suspect’s brothers has been arrested in Belgium and another brother died in the attack, the first official said.

French police have issued a wanted notice with a photo of Salah Abdeslam, 26. It warns people who see him that he is dangerous, saying “do not intervene yourself.”

Police in France are looking for Salah Abdeslam, 26, in connection with the terrorist attacks.

Police in France are looking for Salah Abdeslam, 26, in connection with the terrorist attacks.

Adbeslam slipped past police at a border checkpoint, CBS2’s Matt Kozar reported.

Seven people were detained Sunday in Belgium in connection with deadly attacks in Paris as the city entered three days of mourning for the 129 people killed in the worst violence in France in decades.

French troops deployed by the thousands, and tourist sites were shuttered in one of the most visited cities on Earth as more details of the investigation emerged.

The Islamic State group claimed responsibility for Friday’s gun and bomb attacks on a stadium, a concert hall and Paris cafes that also wounded 350 people, 99 of them seriously.

As many as three of the seven suicide bombers who died in the attacks were French citizens, as was at least one of the men arrested in neighboring Belgium.

PHOTOS: France, World Mourn Deadly Paris Terror Attacks

A French police official said a suicide attacker identified by a skin sample was believed to be living in the Paris suburbs before the attacks. A Belgian official said two of the seven people wired with suicide vests were French men living in Brussels, and among those arrested was another French citizen living in the Belgian capital.

The new information stoked fears of homegrown terrorism in a country that has exported more jihadis than any other in Europe. All three gunmen in the January attacks on the Charlie Hebdo newspaper and a kosher supermarket in Paris were French.

This time, three teams of attackers were involved and seven suicide bombers blew themselves up — three near the stadium, three at the concert hall and one not far from it, authorities said.

A Brussels parking ticket found inside the Volkswagen Polo parked outside the Bataclan concert hall led to one of the men arrested in Belgium, according to a French police official.

Police identified the print on a recovered finger to be 29-year-old Frenchman Ismael Mostefai, a petty thief with ties to radical Islam. Police detained and questioned his relatives.

Three Kalashnikovs rifles were found inside the other car known to have been used in the attacks, a Seat found in Montreuil, a suburb nearly 4 miles east of the French capital, according to the police official, who could not be named because the investigation is ongoing.

Another official in Belgium said the seven people detained would learn later Sunday whether they would be held in custody longer. Three other people were arrested there Saturday.

That official, who spoke on condition of anonymity due to the ongoing investigation, also said two of the seven attackers who died in Paris on Friday night were French men living in Brussels. He said one was living in the Molenbeek neighborhood, which is considered a focal point for religious extremism and fighters going to Syria.

Security was heightened across France, across Europe’s normally open borders, even across the ocean in New York, and how to respond to the Paris attacks became a key point among U.S. Democratic presidential hopefuls at a debate Saturday night.

President Barack Obama on Sunday called the terror attacks in Paris an “attack on the civilized world.”

Obama, speaking at the G-20 summit in Turkey focusing on fighting terrorism, pledged U.S. solidarity with France in the effort to hunt down the perpetrators and bring them to justice.

At the request of France, the European Union will hold a special meeting of its interior and justice ministers Friday to assess the impact of the Paris attacks.

In Paris, the shining sun and warm air felt cruelly incongruous.

Streets, parks and commerce were unusually empty for such a mild, clear day, and several city monuments were closed for security reasons or to express the city’s grief.

Some Parisians and tourists defied the high security, walking past heavily-armed soldiers in body armor to take pictures beneath the Eiffel Tower.

In its statement claiming responsibility, the Islamic State group called Paris “the capital of prostitution and obscenity” and mocked France’s air attacks on suspected IS targets in Syria and Iraq.

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