French President Francois Hollande was expected to hold talks on Thursday with Russian leader Vladimir Putin as part of his diplomatic marathon to forge a broad coalition against Islamic State (IS) jihadists in the wake of the Paris attacks.

The French leader already has the support of Britain, whose prime minister David Cameron set out his case on Thursday for airstrikes against the IS group in Syria, telling lawmakers that his country could not "sub-contract" its security to allies.

Hollande has so far won few concrete pledges during a whirlwind diplomatic tour seeking to intensify efforts to crush the IS in Iraq and Syria, and his bid has been further complicated by a spat between Russia and Turkey over a downed jet.

Before heading to Moscow, Hollande met Italian Prime Minister Matteo Renzi in Paris, who offered only vague support for "a coalition of greater and greater strength that is up to the task of ... the destruction of Daesh," using another name for the IS.

Renzi warned that Libya could be the "next emergency" and said a solution was urgently needed to its political crisis, which has fueled the growth of an IS affiliate close to Europe's southern border.

France last week invoked a clause requiring EU member states to provide military assistance after the November 13 attacks by the IS in Paris that claimed 130 lives.

German Chancellor Angela Merkel on Wednesday pledged to stand beside France after talks with Hollande, saying she would act "swiftly" to see how her country can help.

In Berlin, Defense Minister Ursula von der Leyen said Germany would send 650 soldiers to Mali to provide some relief to French forces fighting jihadists there.

Cameron travelled to Paris on Monday and offered France the use of a British air base in Cyprus for flying missions against the jihadists.

But Hollande received a cooler response from US President Barack Obama when he flew to Washington on Tuesday, with the US reluctant to intensify military action in Syria without a clear strategy or political track in place. 

No 'articulate apology'

Hollande's diplomatic efforts suffered a blow after Turkey shot down a Russian jet on Tuesday.

Turkey's military said the following day it did not know the jet was Russian and that it was ready for "all kinds of cooperation" with Russia, after Moscow called the incident a "planned provocation."

The sole surviving pilot said he received no warning and the aircraft did not violate Turkish airspace, but the Turkish military  released audio recordings claiming to show the Russian jet was repeatedly warned to change course.

"We still have not heard any articulate apologies from Turkey's highest political level nor any proposals to compensate for the harm and damage," Putin told Russian TV on Thursday.

While Moscow conspicuously ruled out any military retaliation against NATO member Turkey, Prime Minister Dmitry Medvedev said he had given ministers two days to work out "a system of response measures" in the economic and humanitarian spheres. He said the broad punitive steps could include halting joint economic projects, restricting financial and trade transactions and changing customs duties.

Russia also attacked Turkey's agricultural sector, tightening checks on food imports over alleged safety standard violations.  

The move could have a major impact on the economy of Turkey, which over the past 10 months has exported agricultural produce and food worth just over $1 billion to Russia.

Russian Foreign Minister Sergei Lavrov has backed Hollande's proposal to close off the Syria-Turkey border, considered the main crossing point for foreign fighters seeking to join the IS. 

Meanwhile, the manhunt continued for two fugitives accused of taking part in the Paris attacks: Belgian-born Frenchman Salah Abdeslam and Belgian-Moroccan Mohamed Abrini.