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 20 bombs in the biggest air strikes since France extended its bombing campaign against the extremist group to Syria in September, a Defense Ministry statement said. The jets launched from sites in Jordan and the Persian Gulf, in coordination with US forces.

As police announced seven arrests and hunted for more members of the sleeper cell that carried out the Paris attacks that killed 129 people, 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 Nov 14, 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 theater where so many died.

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 authorization to publicly disclose such details.

Tantalizing 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 officials also said that a sleeper cell in France then met with the attackers after their training and helped them execute the plan.

There were 24 people involved in the operation, they said: 19 attackers and five others in charge of logistics and planning.

France plans to go ahead with a global climate change summit in Paris at the end of the month, the prime minister said on Nov 14.

The conference "will be held because it's an essential meeting for humanity", Prime Minister Manuel Valls told TF1 television.

About 118 world leaders are expected to attend the opening day of the Nov. 30-Dec. 11 conference, where a global deal to limit greenhouse gas emissions is expected.