France on Monday launched the first air strikes from its aircraft carrier in the Mediterranean as global efforts to combat the Islamic State group gathered pace and world leaders met for talks on the Syrian conflict.

British Prime Minister David Cameron said he would make his case to parliament on Thursday to join the coalition striking IS in Syria.

That followed a morning meeting with President Francois Hollande during which he praised France's decision to ramp up strikes against the jihadist group after the Paris attacks.

"It's my firm conviction that Britain should do so too," Cameron said.

In the first sorties from the Charles de Gaulle aircraft carrier on Monday, newly deployed in the eastern Mediterranean, France bombed IS targets in the Iraqi cities of Ramadi and Mosul, followed by air raids in Syria.

The Iraq strikes were "in support of ground forces that were pushing against troops of (the Islamic State group)," said army chief of staff General Pierre de Villiers, aboard the carrier.

The defence ministry announced Monday evening that four Rafale jets from the aircraft carrier had also joined a mission carrying out bombing raids against IS targets in the group's Syrian stronghold of Raqa.

The strikes took place at 1830 GMT and "destroyed an active site occupied by terrorist fighters in Raqa," the ministry said.

A week of frantic international diplomacy meanwhile was under way with Hollande set to meet all five permanent members of the UN Security Council, and the United States trying to rally support for a ceasefire in Syria.

Major differences remain over the future of Syrian President Bashar al-Assad. Western powers want him removed from power, but he retains strong support from old allies Russia and Iran.

In his first visit to Iran for eight years, Russian President Vladimir Putin met with Iran's supreme leader Ayatollah Ali Khamenei on Monday.

They emphasised their opposition to any "external attempts" to bring regime change in Syria, a Kremlin official said.

At the same time, US Secretary of State John Kerry was in Abu Dhabi hoping to forge a coalition of Syrian opposition groups for peace talks.

Kerry hopes his Emirati and Saudi allies can pressure rebel factions into accepting a ceasefire with Assad within "a few weeks" -- a step seen as crucial to refocusing the war on IS.

"You can be confident that the diplomatic front is in high gear, with a very real plan on the table to be implemented," Kerry said.

- Defining week -

In Paris, Cameron and Hollande stood side by side after laying a wreath at the Bataclan concert hall, where 90 of the 130 victims were killed in the Paris attacks of November 13.

While Britain has joined US-led coalition strikes on IS in Iraq, it has so far held back from hitting targets in Syria, where the jihadists also hold large swathes of territory.

The British leader said he had offered France the use of a strategically located British airbase in Cyprus, RAF Akrotiri, to facilitate air strikes, and assistance with refuelling French jets.

Hollande, who has said France is in a "war" against the jihadists, is embarking on what could be a defining week of his three-year-old presidency.

On Tuesday, he will fly to Washington for talks with President Barack Obama, and will meet German Chancellor Angela Merkel and Italian Prime Minister Matteo Renzi in Paris over the next two days.

Completing a series of meetings with each of France's fellow UN Security Council members, Hollande will travel to Moscow for talks with Putin on Thursday and hold a working dinner with Chinese President Xi Jinping in Paris on Sunday.

The Security Council on Friday authorised countries to "take all necessary measures" to fight IS in a resolution that won unanimous backing in the wake of the bloodshed in Paris.

Hollande said he hoped the resolution would "help mobilise nations to eliminate Daesh", using an alternative name for IS.

The US-led coalition has been pounding IS targets in Syria for over a year, but France joined the campaign only in September and has concentrated its air strikes on the city of Raqa.

Russia has also bombed IS targets but has attracted criticism from Western powers for bombing other rebel groups opposed to Assad, a long-time ally of Moscow.

Iran has been Assad's other main backer since an uprising broke out against his rule in 2011 and escalated into a brutal civil war.

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KERRY GROUP

Cameron International