Paris - France launched "massive" air strikes on the Islamic State group's de-facto capital in Syria on Sunday night, destroying a jihadi training camp and a munitions dump in the city of Raqqa, where Iraqi intelligence officials say the attacks on Paris were planned.Twelve aircraft including 10 fighter jets dropped a total of 20 bombs in the biggest air strikes since France extended its bombing campaign against the extremist group to Syria in September, a Defence Ministry statement said. The jets launched from sites in Jordan and the Persian Gulf, in coordination with US forces.Meanwhile, as police announced seven arrests and hunted for more members of the sleeper cell that carried out the Paris attacks, French officials revealed to The Associated Press that several key suspects had been stopped and released by police after the attack.The arrest warrant for Salah Abdeslam, a 26-year-old born in Brussels, calls him very dangerous and warns people not to intervene if they see him.Yet police already had him in their grasp early on Saturday, when they stopped a car carrying three men near the Belgian border. By then, hours had passed since authorities identified Abdeslam as the renter of a Volkswagen Polo that carried hostage takers to the Paris theatre where so many died.‘Suspect let go’Three French police officials and a top French security official confirmed that officers let Abdeslam go after checking his ID. They spoke on condition of anonymity, lacking authorisation to publicly disclose such details.Clues about the extent of the plot have emerged from Baghdad, where senior Iraqi officials told the AP that France and other countries had been warned on Thursday of an imminent attack.An Iraqi intelligence dispatch warned that Islamic State group leader Abu Bakr al-Baghdadi had ordered his followers to immediately launch gun and bomb attacks and take hostages inside the countries of the coalition fighting them in Iraq and Syria.The Iraqi dispatch, which was obtained by the AP, provided no details on when or where the attack would take place, and a senior French security official told the AP that French intelligence gets these kinds of warnings "all the time" and "every day."However, Iraqi intelligence officials told the AP that they also warned France about specific details: Among them, that the attackers were trained for this operation and sent back to France from Raqqa, the Islamic State's de-facto capital.The officials also said that a sleeper cell in France then met with the attackers after their training and helped them to execute the plan. There were 24 people involved in the operation, they said: 19 attackers and five others in charge of logistics and planning.None of these details have been corroborated by officials of France or other Western intelligence agencies.All these French and Iraqi security and intelligence officials spoke with the AP on condition of anonymity, citing the ongoing investigation.Three brothers involvedAbdeslam is one of three brothers believed to be involved; one who crossed with him into Belgium was later arrested, and another blew himself up inside the Bataclan theatre after taking the audience hostage and firing on them repeatedly. It was the worst of Friday's synchronized attacks, leaving 89 dead and hundreds of people wounded inside.The Islamic State group claimed responsibility. Its statement mocked France's air attacks on suspected ISIS targets in Syria and Iraq, and called Paris "the capital of prostitution and obscenity."In all, three teams of attackers including seven suicide bombers attacked the national stadium, the concert hall and nearby nightspots. The attacks wounded 350 people, 99 of them seriously.Abdeslam rented the black Volkswagen Polo used by the hostage-takers, another French security official said. A Brussels parking ticket found inside led police to at least one of the arrests in Belgium, a French police official said.Three Kalashnikovs were found inside another car known to have been used in the attacks that was found in Montreuil, an eastern Parisian suburb, another a French police official said.