French police commandos fired more than 5,000 shots into an apartment near Paris on Wednesday during a raid against a heavily armed jihadist group that lasted seven hours and turned the area into a war zone.

The fighting was so intense that not only were the police unable to identify the bodies of the militants after they had finally entered the apartment, but they could not even determine whether two or three people had died during the assault.

With forensic experts still scouring the building in the St. Denis suburb north of the capital, the Paris chief prosecutor and the police chief who leads the crack RAID commandos spoke of a complex operation that ran into problems from the word 'go'.

A contingent of 70 commandos, backed up by 40 other police, surrounded the building before dawn following a tip-off that Abdelhamid Abaaoud, a Belgian militant accused of masterminding last week's attacks in Paris, might be hiding there.

They stormed the property on Rue du Corbillon at 4:16 a.m. (0316 GMT), heading for an apartment on the third floor.

"The security door didn't give way when the first RAID (explosive) charges went off, which gave the terrorists time to prepare themselves," prosecutor Francois Molins told reporters.

Jean-Michel Fauvergue, the RAID chief, told Le Figaro newspaper that the trapped suspects had wheeled a heavy barricade in front of the door before opening fire on their assailants.

"Hundreds of shots were exchanged. The terrorists even threw grenades," he said, adding that the shooting became more sporadic after about 45 minutes.

As quiet descended, a police attack dog was sent in to check for signs of life, but was shot dead.

By that stage, police sharpshooters had positioned themselves so that they could see into all the windows and doors. One saw a militant and told him to raise his hands. He didn't, Fauvergue said, so the order was given to shoot him.

However, he was only wounded and continued to fire back.

SPINAL CORD

A women started to fire repeatedly and there was then a huge blast. Police said she had set off an explosive vest, but Molins said further analysis was needed to know how the vest detonated.

"The windows overlooking the road shattered. Bits of a body, part of a spinal cord, fell onto one of our cars," Fauvergue said. A source close to the investigation told Reuters they believed the woman was Abaaoud's cousin.

Firing continued from inside, so Fauvergue said police threw roughly 20 grenades, each containing 40 grams (1.4 ounces) of explosives, into the apartment.

They then tried to get robots with cameras into the shattered rooms, but there was too much rubble blocking their way. Realising that part of the floor had collapsed, they went down to the apartment below to push up probes.

There they found a body that had fallen through the masonry. Molins said it was so riddled with bullets and shrapnel that it was impossible to carry out an identification.

Returning to the third floor, police discovered two men hiding under laundry, who were arrested. In total, seven men and one woman were arrested in and around the building.

With no more movement detected from inside, police finally entered the apartment.

A judicial source said initial tests on body parts found in the apartment suggested that the DNA of three separate individuals was present, but further checks were needed.

Five police were injured in the assault, none seriously.

"It was a particularly dangerous and difficult police operation," President Francois Hollande said, adding that the security forces had "undoubtedly underestimated the violence that would await them". – Reuters