By Chine Labbé and Crispian Balmer

PARIS (Reuters) – France and Russia staged air strikes on Islamic State targets in northern Syria on Tuesday, punishing the group for attacks in Paris and against a Russian airliner that together killed 353 people.

Islamic State has claimed responsibility for a coordinated onslaught in Paris on Friday and the downing of a Russian charter jet over Sinai on Oct. 31, saying they were in retaliation for French and Russian air raids in Iraq and Syria.

Still reeling from the Paris carnage that killed 129, most of them young people, France formally requested European Union assistance in its fight against the militants and British Prime Minister David Cameron edged closer to extending military action against Islamic State in Syria.

Police investigating the worst atrocity in France since World War Two discovered two safe houses in Paris where they believe the militants launched their assault. Underlining the widening scope of the probe, police in Germany said they arrested five suspects, including two women.

In Moscow, the Kremlin acknowledged that a bomb had destroyed a Russian airliner last month, killing 224 people. President Vladimir Putin vowed to hunt down those responsible and intensify air strikes against Islamists in Syria.

“Our air force’s military work in Syria must not simply be continued,” he said. “It must be intensified in such a way that the criminals understand that retribution is inevitable.”

Western officials said Russia launched a “significant number” of strikes in Syria on Tuesday hitting the Islamic State stronghold of Raqqa. In a separate action, apparently not coordinated, French warplanes targeted Raqqa for a second day.

French President Francois Hollande has said he will see Putin and U.S. President Barack Obama in the coming days to try to convince them to join a grand coalition against Islamic State which controls swathes of Syria and Iraq.

Russia began air strikes in Syria at the end of September. It has always said its main target is Islamic State, but most of its bombs in the past have hit territory held by other groups opposed to its ally, Syrian President Bashar al-Assad.

MANHUNT

In Brussels, Defence Minister Jean-Yves Le Drian invoked the EU’s mutual assistance clause for the first time since the 2009 Lisbon Treaty introduced the possibility, saying he expected help with French operations in Syria, Iraq and Africa.

“This is firstly a political act,” Le Drian told a news conference after a meeting of EU defense chiefs.

The 28 EU member states accepted the French request but it was not immediately clear what assistance would be forthcoming.

A manhunt was continuing in France and Belgium on Tuesday for one of the eight attackers in the Paris assault.

French police staged 128 raids overnight in the hunt for accomplices and Islamist militant networks, Interior Minister Bernard Cazeneuve said. Police found a third Belgian-licensed car believed to have been used by the attackers and sealed off the area around it in Paris’ 18th district.

Cazeneuve told France Info radio police were making rapid progress in their investigation but declined to give details.

One top suspect, Frenchman Salah Abdeslam, 26, remains at large after escaping back to Belgium early on Saturday and eluding a police dragnet in the Brussels neighborhood of Molenbeek, where he lived with his two brothers.

One of the brothers blew himself up outside a Paris cafe on Friday, seriously injuring many bystanders.

Hollande, who has declared a state of emergency, met visiting U.S. Secretary of State John Kerry on Tuesday to press his call for the U.S.-led and Russian-led coalitions to join forces.

Kerry told reporters afterwards that Islamic State was losing territory in Syria and Iraq, but said increased co-ordination with Moscow would require progress in a political drive to end the war. That process is complicated by a U.S. demand that Assad steps down as president.

“DON’T SCAPEGOAT REFUGEES”

The U.N. refugee agency and Germany’s police chief urged European countries not to demean or reject refugees because one of Friday’s Paris bombers was believed to have slipped into Europe among migrants registered in Greece.

“We are deeply disturbed by language that demonizes refugees as a group,” U.N. spokeswoman Melissa Fleming said after government officials in Poland, Slovakia and the German state of Bavaria cited the Paris attacks as a reason to refuse refugees.

The head of Germany’s Federal Criminal Office said there was no sign that Islamist militants had entered Germany posing as an asylum seeker to commit an attack.

French Prime Minister Manuel Valls said Paris would spare no expense to reinforce and equip its security forces and law enforcement agencies to fight terrorism, even though that was bound to involve breaching European budget deficit limits.

“We have to face up to this, and Europe ought to understand,” he told France Inter radio.

The European Commission said it would show understanding to France if additional security spending pushed up its deficit.

As France geared up for a long war, the British prime minister said he would present a “comprehensive strategy” for tackling Islamic State to parliament. British war planes have been bombing the militants in Iraq, but not Syria.

“It is in Syria, in Raqqa, that Isil has its headquarters and it is from Raqqa that some of the main threat against this country are planned and orchestrated,” Cameron said, referring to Islamic State by one of its many acronyms.

“Raqqa, if you like, is the head of the snake.”

French prosecutors have identified five of the seven dead assailants from Friday night — four Frenchmen and a foreigner fingerprinted in Greece among refugees last month.

In addition to the suspect on the run, police believe at least four other people helped organize the mayhem.

Investigators believe the attacks may have been ordered by Abdelhamid Abaaoud, a Belgian national now living in Syria where he has become an Internet propagandist for Islamic State under the nom de guerre Abu Omar al-Belgiki — the Belgian.

Belgian media have reported that Salah Abdeslam spent time in jail for robbery five years ago alongside Abaaoud.

Police in France named two of the French attackers as Ismael Omar Mostefai, 29, from Chartres, southwest of Paris, and Samy Amimour, 28, from the Paris suburb of Drancy.

France believes Mostefai, a petty criminal who never served time in jail, visited Syria in 2013-2014. His radicalization underlined the trouble police face trying to capture an elusive enemy raised in its own cities.

(Additional reporting by Laurence Frost, Maya Nikolaeva, Julien Ponthus, Patrick Vignal and David Brunnstrom; Writing by Paul Taylor and Crispian Balmer; Editing by Sonya Hepinstall)