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 Friday’s 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 Defense Ministry statement said. In France, 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 also revealed to the Associated Press that several key suspects had been stopped and released by police after the attack. Three French police officials and a top French security official confirmed that officers let Abdeslam go after checking his ID. 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. [...] Iraqi intelligence officials said they also warned France about specific details: among them, that the attackers were trained for this operation and sent back to France from Raqqa. Three Kalashnikov automatic rifles 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. Struggling to keep his country calm and united after an exceptionally violent year, President Francois Hollande met Sunday with opposition leaders — conservative rival and former President Nicolas Sarkozy as well as increasingly popular far-right leader Marine Le Pen, who has used the attacks on Paris to advance her anti-immigrant agenda. Refugees fleeing war by the tens of thousands fear that the Paris attacks could prompt Europe to close its doors, especially after police said a Syrian passport found next to one attacker’s body suggested its owner passed through Greece into the European Union.