ST.-DENIS, France — The prosecutor overseeing the investigation into the Paris terrorist attacks said Wednesday night that the authorities were trying to determine whether Abdelhamid Abaaoud, the Belgian militant suspected of being the ringleader, died in a police raid hours earlier on an apartment in the northern Paris suburb of St.-Denis.
At least two people died in the operation — a young woman who set off an explosive vest, and a person whose body was riddled with gunfire and shrapnel — and eight were arrested.
The prosecutor, François Molins, said that Mr. Abaaoud and another fugitive, Salah Abdeslam, were not among those arrested. But he said the authorities were not certain about the number of dead, or their identities, leaving open the possibility that either or both men might still be on the run. “As I speak, I am unable to give you a definitive number and identities of people killed,” he said.
Mr. Molins said the fighting was so intense — the police fired more than 5,000 rounds of ammunition, and a gun battle went on with hardly any interruption for nearly an hour, he said — that it could take some time for the authorities to determine what had happened inside the building, which was at risk of collapse.
Mr. Molins said the assault was one result of an investigation that is gathering steam. “A new team of terrorists was neutralized, and all elements suggest that with regards to their armament, their structured organization and their determination, this commando group could have taken action,” he said.
The raid, on the Rue du Corbillon, began around 4:15 a.m. Paris time, when special police forces, backed by truckloads of soldiers, cordoned off an area near the Place Jean Jaurès, a main square in the medieval heart of St.-Denis — not far from the Stade de France, the stadium where three attackers blew themselves up on Friday.
The police shouted at pedestrians to get off the street or seek cover; officers even broke through the door of a small church, St.-Denys de l’Estrée, chasing down what turned out to be a false lead. The raid was so intense that the building was at risk of collapse; workers had to shore it up to prevent it falling.
The police operation transfixed a country still reeling from the attacks, the worst terrorist assault in Western Europe since 2004; officials said on Wednesday that they had finally completed the grim task of positively identifying all 129 of the people who were killed. Soldiers patrolled La Défense, the business district west of Paris. Two flights to Charles de Gaulle Airport were diverted because of a security scare there.
Bernard Cazeneuve, the interior minister, announced that the police had conducted 414 raids across the country over the past three nights. Sixty people have been arrested and detained, and 75 weapons seized, including 11 heavy weapons, 33 long firearms and 31 handguns, the statement said. An additional 118 people were put under house arrest.
The news that Mr. Abaaoud was the target of the raids came as something of a revelation. Intelligence officials in both France and the United States had said on Tuesday that they believed that Mr. Abaaoud was in Syria — where he traveled last year to fight for the Islamic State, and lured his 13-year-old brother to join him. It now appears that he may have been in Europe all along.
Mr. Molins said the raid resulted from the intense investigation that began after the attacks on Friday night, but he did not say whether it was intended to thwart another attack, or what Mr. Abaaoud might have been doing in St.-Denis.
“A lot of work was done as part of this investigation, which made it possible to obtain, through phone records, surveillance and testimony, elements that could have suggested that the man named Abaaoud was potentially in an apartment used for plotting in St.-Denis,” he said.
A man arrested during the police operation on Wednesday later told Agence France-Presse that he had lent the apartment to the men as a favor to a friend. “I said that there was no mattress, they told me, ‘It’s not a problem,’ they just wanted water and to pray,” the man was quoted as saying, before he was handcuffed and led away by the police.
The police operation unfolded over nearly seven hours, with an initial series of explosions followed by sporadic bursts of gunfire. A government spokesman declared on Twitter at 11:47 a.m. that the operation was over. Five police officers were lightly wounded, and a 7-year-old police dog, a Malinois named Diesel, was killed.
Mr. Cazeneuve said the 110 police officers involved had been “extremely brave” during the operation, “enduring gunfire for many hours, in conditions that they had never encountered until now.” He also praised the inhabitants of St.-Denis for their calm.
St.-Denis, a city of 118,000, is known for its melting-pot population and large Muslim community, as well as a Gothic basilica where many French monarchs are buried.
Djamila Khaldi, a 54-year-old cashier who lives near the basilica, was preparing to take her daughter to the airport when the gunfire erupted.
Ms. Khaldi said she was not surprised the police had tracked the suspects to the neighborhood. She said a friend of hers believed she had seen one of the wanted men, Salah Abdeslam, on Monday.
“She was terrified, and she looked at another woman knowing that she recognized him too,” Ms. Khaldi said. “They did not dare to go to the police.”
Didier Paillard, the mayor of St.-Denis, said the Rue du Corbillon, where the raid occurred, had “many buildings and habitats in a disgraceful state,” with some apartments lacking even electricity and running water. “We were not prepared for this discovery,” he said of the raid. “This is a city that has 130 different nationalities, including people who come from war zones. We are a population that needs serenity.”
Prime Minister Manuel Valls, Defense Minister Jean-Yves Le Drian and Justice Minister Christiane Taubira joined President François Hollande and Mr. Cazeneuve, the interior minister, at the Élysée Palace to monitor the operation.
Afterward, Mr. Hollande told a conference of French mayors that the raid in St.-Denis “confirms that we are at war.” He said he would travel to Washington next week to meet President Obama, and to Moscow two days later to meet President Vladmir V. Putin of Russia, to discuss the formation of “a large coalition” to act “decisively” against the Islamic State, which is also known as ISIS or ISIL.
“Daesh has financial and oil resources, and has created young radical Islamists through complicity in Europe and within our own country,” Mr. Hollande told the gathering, using the Arabic acronym for the Islamic State.
“Their attacks bloodied Paris and St.-Denis,” he added, “but it is the entire country that has been attacked.”
Mr. Hollande declared a state of emergency on Friday and has sought sweeping new authorities, including constitutional amendments, which he says would make it easier to fight terrorism. On Wednesday, he said the government would help the mayors equip and arm local police officers. He also said that the government was introducing legislation that would make it possible to “immediately” dissolve organizations that glorify terrorism.
“I say it firmly, France will remain the country of liberty, of movements, of culture,” he said. “An active, valiant, dynamic country.”
“What would France be without its museums, without its terraces, without its concerts, without its sports competitions?” he added.
But even as parts of France have started to return to normal life, the raids in St.-Denis were a reminder of the nationwide dragnet that continues.
Clues that have emerged since the attacks suggest that they required careful planning around weapons, transportation, communications and logistics.
Some of the attackers rented a house in the northeast Paris suburb of Bobigny last week, telling the landlady they were businessmen from Belgium, and a hotel suite in the southeast Paris suburb of Alfortville, officials said. A French official who was briefed on the investigation but was not authorized to discuss it said that a cellphone found in a trash can near the Bataclan concert hall, where 89 people died on Friday, had led the police to the Alfortville hotel. The phone contained a text message — “on est parti on commence’’ — that loosely translates as “here we go, we’re starting” or as “we have left, we’re starting.”
On Tuesday morning, the authorities seized a black Renault Clio with Belgian license plates in the 18th Arrondissement, near the suburb of St.-Denis, where three suicide bombers detonated their explosives during a soccer game at the Stade de France. The authorities are looking into the possibility that the vehicle might have been intended for yet another attack.
On Tuesday night, the authorities released a photo of one of the stadium bombers — who used a Syrian passport to enter Greece last month, evidently posing as a migrant — and asked for the public’s help in identifying him. The passport was probably stolen, and the identity on the passport page — Ahmad al-Mohammad, 25, of Idlib, Syria — may be that of a dead Syrian soldier, the French official said.
Belgium, where Mr. Abaaoud is believed to have organized the attacks, remained on a state of high alert on Wednesday, as the authorities continued to search for Salah Abdeslam, who is thought to have been part of the plot. (His brother Ibrahim was one of the seven attackers who died on Friday.)
The number of federal police officers patrolling Brussels will be doubled starting Thursday, to 40 from 20 during the day, and to 30 from 15 at night, Interior Minister Jan Jambon announced.
Molenbeek, a working-class Brussels neighborhood, was the base for Mr. Abaaoud, the suspected plotter, and for the Abdeslam brothers. (A third brother, Mohamed, who lives there, was not involved in the attacks and has pleaded for Salah to turn himself in.)
Salah Abdeslam was thought to have escaped to Brussels after the attacks. He has been the subject of an intense international manhunt. The authorities said on Tuesday that they were looking for a second fugitive; it turns out that man is Mr. Abaaoud.
The Belgian authorities have charged two men — Hamza Attou, 21, a Brussels native, and Mohamed Amri, 27, who was born in Morocco — with participating in a terrorist activity, saying they drove Salah Abdeslam to Brussels from Paris.