French warplanes pounded Islamic State's Syrian stronghold Sunday in retaliation for a wave of coordinated attacks claimed by the jihadists which left 129 people dead in Paris.
As the nation prepared to mourn the victims with a minute of silence Monday, French police released a photograph of a suspect also wanted in Belgium where it is suspected the attacks may have been planned.
In the first strikes since Friday's carnage which killed at least 129 and wounded more than 350, French warplanes bombed IS targets in Raqa, the Islamists' de facto capital in Syria.
The raid destroyed an IS command post, jihadist recruitment centre, a munitions depot and a "terrorist" training camp, the defence ministry said.
The operation was conducted in coordination with US forces by a dozen aircraft which took off from Jordan and the United Arab Emirates, it said.
President Francois Hollande has denounced the Paris attacks -- the worst in the country's history -- as an "act of war" and vowed to hit back against Islamic State "without mercy".
- 'Dangerous' suspect -
French police said they were seeking a "dangerous" suspect, 26-year-old Salah Abdeslam who is said to be one of three brothers linked to the slaughter.
He is believed to be either on the run or one of the gunmen who died during the attacks, security sources said. He lived in the poor immigrant Brussels neighbourhood of Molenbeek, where Belgian police made several arrests in connection with the Paris attacks.
"We are determined to act together... to dismantle the networks" of the jihadists, French Interior Minister Bernard Cazeneuve said after talks Sunday with his Belgian counterpart Jan Jambon.
As the investigation spread across Europe, police Sunday evening carried out a search in Bobigny, in the northern suburbs of Paris, but the results were not yet known.
Prosecutors said they believed three groups of attackers were involved in the carnage, and they did not rule out that one or more assailants may still be at large.
The heavily armed gunmen wearing explosive vests opened fire on crowds enjoying a Friday night at outdoor cafes and at the Bataclan concert hall, scene of the worst carnage where 89 people were killed as they watched a gig by the Eagles of Death Metal group.
Seven of the gunmen and suicide bombers died in the bloodshed, with three blowing themselves up outside the Stade de France as the French and German football teams were playing a friendly.
As night fell over the jittery French capital on Sunday, crowds shocked by the brutality of the killings packed into the Notre-Dame cathedral to mourn the dead.
Museums and parks were closed and Sunday markets were empty, although thousands still flocked to lay flowers and light candles at the sites of the violence.
But in a sign of just how shaken people are, the sound of fire-crackers at Place de la Republique, where mourners were standing in quiet solidarity, sent scores fleeing in panic before they realised it was a false alarm.
- France in mourning -
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France will observe a minute of silence at noon (1100 GMT) Monday, which the European Union wants all member states to respect. In the United States, the Stars and Stripes will fly at half-mast at the White House and other official buildings until sunset Thursday.
Hollande will observe the silence at the Sorbonne University, in recognition of the large number of young victims, as Paris struggles to come to terms with the atrocities that come 10 months after jihadists hit satirical magazine Charlie Hebdo and a Jewish supermarket.
In an outpouring of solidarity, more emotional vigils were held across the globe over the weekend. In Rome the lights of the Trevi Fountain and the Colossuem were turned off Sunday night in a silent tribute.
And in a striking gesture, the great pyramid in Egypt was bathed in French, Lebanese and Russian colours in homage to the victims in Paris as well as those in the Beirut bombings, and the Sinai plane crash.
French authorities have so far identified more than 100 of the dead, who included journalists, lawyers, students, parents of small children.
More than 25 foreigners from over a dozen countries were among the victims, with the first American fatality confirmed as California State University student Nohemi Gonzalez, 23, who died in the shootout at the Petit Cambodge restaurant.
- Belgian connection -
It is now known that three of the suicide bombers were French nationals, two of whom lived in the Belgian capital Brussels.
In a further sign of the growing Belgian connection to the attacks, investigators said two cars used in the violence were hired there.
One was found near the Bataclan venue, and the other in the suburb of Montreuil east of Paris, with a number of AK47 rifles inside.
Witnesses said the second car, a black Seat, was used by the gunmen who shot dozens of people in bars and restaurants in the tendy Canal St Martin area of Paris.
The first attacker to be named by investigators was Omar Ismail Mostefai, a 29-year-old father and French citizen, who was identified by a severed finger found among the carnage at the Bataclan.
Meanwhile, the discovery of a Syrian passport near the body of one suicide attacker has raised fears that some of the assailants might have entered Europe as part of the huge influx of people fleeing Syria's civil war.
Greek and Serbian authorities have confirmed the passport was issued to a man who registered as a refugee in October on the island of Leros and applied for asylum in Serbia a few days later.
But European Commission President Jean-Claude Juncker, who has urged EU countries to take in more refugees, said there was no need for a complete review of the bloc's policies.
"Those who organised, who perpetrated the attacks are the very same people who the refugees are fleeing and not the opposite," he said.
The Islamic State group said it carried out the attacks in revenge for French air strikes in Syria and threatened further violence in France "as long as it continues its Crusader campaign".
World leaders united Sunday to denounce terrorism at a heavily guarded G20 summit in Turkey and observed a minute's silence for those killed.