ST.-DENIS, France — The assault began before dawn Wednesday at a decrepit squat in a close suburb of Paris when scores of French police officers stormed a third-floor apartment in search of their elusive quarry: Abdelhamid Abaaoud, a Belgian suspected of organizing last week's deadly attacks by the Islamic State in Paris.
To get through a reinforced door, the police had to set explosives, giving the people inside time to prepare. A furious firefight ensued, with the police unleashing 5,000 rounds over the next hour and employing snipers and grenades. A female suicide bomber exploded her vest, collapsing the floor.
When it was all over, the police had swept eight people into custody and found at least two mangled bodies. Abaaoud had not been taken alive, the authorities said — and it was not clear whether one of the bodies was his.
"I am not able to give you the definitive number and identities of the people who were killed," the Paris prosecutor, François Molins, said, adding that neither Abaaoud nor Salah Abdeslam, another suspected Paris attacker who has been on the loose, was among those arrested.
The day of further violence left Paris on edge once again and much of the world transfixed as the manhunt for Abaaoud and his accomplices played out. Evening brought only uncertainty about whether the threat had been eradicated or whether Abaaoud, who has boasted of eluding capture, remained at large.
Adding to the confusion was the identity of the female suicide bomber, believed to be the first woman affiliated with the Islamic State to have blown herself up, other than those with Boko Haram, the militant Islamist group in Nigeria. Two French intelligence officials briefed on the investigation said she was believed to be a cousin of Abaaoud, Hasna Aitboulahcen, 26, who worked for a nearby company.
Molins suggested that the raid might have averted another terrorist attack, given the determination and organization shown by the group and the extent of its weaponry.
"This commando group was ready to act," he said.
The breakthrough appeared to have come with a tip on Monday night: Abaaoud, an Islamic State militant linked to a series of previous attacks, was not in Syria, as some intelligence officials had thought, or his native Belgium. If the tip was to be believed, he was in France.
The authorities pored over telephone and banking records, Molins said. One clue led to another, until the authorities concluded that it was likely that Abaaoud was holed up in St.-Denis, the suburb on the northern edge of Paris where the attacks began last Friday night at 9:20 p.m. with a suicide explosion at the nearby national soccer stadium.
At 4:20 a.m. Paris time on Wednesday, police assault teams stormed the three-story building on the Rue du Corbillon, which local officials and neighbors described as a drug-infested and dangerous street that has many squatters.
Backed by truckloads of soldiers, 110 officers from two special police units cordoned off an area near the Place Jean Jaurès, a main square in the medieval heart of the city.
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.
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 Abdeslam on Monday.
"She was terrified, and she looked at another woman knowing that she recognized him too," Khaldi said. "They did not dare to go to the police."
The police conducted a simultaneous raid on the nearby Boulevard Carnot, the home of someone identified as having been in contact with the people at the Rue du Corbillon. The apartment was empty and no weapons were found there, but a man and a woman outside the apartment were detained.
Before he was handcuffed and led away by the police, the man 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."
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.
As the raids were being carried out, 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 alarm.
At 11:47 a.m., after more than seven hours, government spokesman Stéphane Le Foll declared that the operation was over. Five police officers were slightly wounded, and a 7-year-old police dog, a Malinois named Diesel, was killed.
Prime Minister Manuel Valls, Defense Minister Jean-Yves Le Drian and Justice Minister Christiane Taubira had joined President François Hollande and Interior Minister Bernard Cazeneuve at the Élysée Palace to monitor the operation.
The raid was just the most spectacular of an aggressive counterterrorism campaign the French government has been conducting since Friday night. Officials said Wednesday that they had identified all 129 of the people who were killed Friday.
Cazeneuve said Wednesday that the police had conducted 414 raids across the country during 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.
Officials have been piecing together the planning for the attacks. They said that some of the plotters had rented a house in the northeast Paris suburb of Bobigny, and others took out a hotel suite in the southeast Paris suburb of Alfortville.
Molins said a cellphone found in a trash can near the Bataclan concert hall, where 89 people died 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."
Molins said investigators had determined that the attackers had arrived in Paris on Thursday in three cars rented by Abdeslam and his brother Ibrahim, who blew himself up in a cafe on Friday night after shooting numerous Parisians in bars and restaurants.
After the raids, Hollande told a conference of French mayors that the operation "confirms that we are at war." He said he would travel to Washington next week to meet President Barack Obama, and to Moscow two days later to meet President Vladimir 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," 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."
Hollande declared a state of emergency on Friday and has sought sweeping new authority, 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.
Belgium, where Abaaoud is believed to have organized the attacks, remained on a state of high alert on Wednesday. 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 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.)
In Molenbeek on Wednesday, some 2,000 people gathered in the market square, not far from where Abaaoud grew up, to mourn the victims of the Paris attacks. Security was tight — police frisked everyone upon entering — but the vigil went on without incident.