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 in Paris by the Islamic State.

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. Mr. 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 Mr. Abaaoud nor Salah Abdeslam, another suspect in the attacks who has been on the loose, was among those arrested.