French warplanes pounded Islamic State targets and Russia vowed to ramp up its bombing campaign in Syria on Tuesday as the devastating attacks on Paris galvanised international resolve to destroy the jihadists and end the Syrian war.

In a grieving Paris, US Secretary of State John Kerry said a "big transition" in Syria was probably only weeks away as he expressed solidarity with the French nation after IS gunmen and suicide bombers massacred 129 people in the capital on Friday night.

Kerry said an agreement between deeply divided countries such as Iran, Russia and Saudi Arabia on a path to elections in Syria at talks held in Vienna Saturday was a "gigantic step", and he expected rapid progress.

"We are weeks away conceivably from the possibility of a big transition for Syria," he said.

The quickening political process came as French President Francois Hollande vowed to pursue IS mercilessly for their "acts of war" and Russia sought vengeance after finally confirming it believed a bomb attack did bring down a Russian passenger jet over Egypt last month that killed 224 people.

The IS group which operates out of Iraq and Syria claimed responsibility for downing the airliner as well as a bombing in Beirut last week.

"My sense is that everybody understands that... we have to step up our efforts to hit them (IS) at the core where they're planning these things," said Kerry.

"We've agreed to exchange more information, and I'm convinced that over the course of the next weeks, Daesh will feel even greater pressure," he added, using another term for IS.

Hollande will visit Washington next week to meet President Barack Obama, and is also planning a meeting with Russian President Vladimir Putin in the coming days.

And as the probe into the horror intensified, French police carried out more than 100 raids for a second night running, as a manhunt continued for 26-year-old Salah Abdeslam, one of two Belgium-based brothers implicated.

- Paris grieves -

In Paris, stunned residents continued to flock to shrines of candles and flowers, while photographs of smiling young victims have been pasted at attack sites or outside their places of work.

The city is palpably more shaken than after the January attacks which killed 17 people at Charlie Hebdo magazine and a Jewish supermarket, but many have defiantly returned to sidewalk terrace cafes where they can be heard poring over the details of the assault.

But a shadow still hangs over the City of Light four days after IS suicide bombers and gunmen struck as Parisians watched a France-Germany football match, a concert by Californian group Eagles of Death Metal, or enjoyed a night out at restaurants and sidewalk cafes.

In the Syrian city of Raqa, the stronghold of IS, French warplanes destroyed a command centre and training centre in its second series of airstrikes in 24 hours, according to Prime Minister Manuel Valls.

Hollande said Monday that the Paris attacks were "decided and planned in Syria, prepared and organised in Belgium (and) perpetrated on our soil with French complicity".

- Russia strikes -

Hollande also said the French aircraft carrier Charles de Gaulle would be deployed to the eastern Mediterranean to "triple our capacity to take action" against IS in Syria.

Russia on Tuesday also staged a "significant number" of air strikes on Raqa.

The focus of the investigation was Salah Abdeslam, whose sibling Brahim blew himself up outside a bar in Paris, seriously injuring one person.

Police found a second car rented by Salah, while his brother was found to have rented an apartment in the gritty Parisian suburb of Bobigny a few days before the attack.

Investigators believe Belgian jihadist Abdelhamid Abaaoud, who is based in Syria and knew Salah Abdeslam, may be the mastermind of the attacks.

Five of the Paris assailants have already been identified, but it is not known how many fled.

- 'Sing for France' -

IS has repeatedly urged assaults on France which has seen a litany of attacks and foiled attacks since January, from a man who beheaded his boss to another who was overpowered as he opened fire on a high-speed train.

The French minister in charge of transport, Segolene Royal, said she wanted security gates at the access of all local and international trains.

This proposal followed a raft of measures unveiled by Hollande in a historic speech to parliament on Monday, in which he called for an extension of the state of emergency by three months and announced 8,500 new jobs to help counter-terrorism.

In the latest outpouring of international empathy for the French trauma, England fans have been urged to join in a rendition of the French anthem La Marseillaise before France return to action in a friendly match against England in London on Tuesday.

The words "Liberte, Egalite, Fraternite" in the colours of the French flag lit up Wembley Stadium, where the match will be played.

Big screens at the stadium will display the words, which were also printed on the back of The Sun and Daily Mirror tabloids.

The Sun instructed readers to "sing for France".

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