Syria war: France to prepare for IS air strikes
President Francois Hollande has ordered preparations to begin for air strikes on Islamic State militants in Syria.
He said France would start reconnaissance flights on Tuesday with a view to launching attacks, but ruled out sending troops on the ground.
Russia has responded to growing concern that it is increasing its military support for President Bashar al-Assad.
More than 220,000 people have been killed and more than nine million displaced in the war in Syria.
Speaking at his bi-annual news conference in Paris, Mr Hollande said terror attacks had been planned from Syria against several countries, including France.
"My responsibility is to ensure that we are informed as much as possible on the threats to our country," he said.
"So I have asked the defence minister that from tomorrow reconnaissance flights begin over Syria that will enable us to consider air strikes against Islamic State."
He said it would be "pointless and unrealistic" for France to send ground troops into the country.
But he added his government would continue to work for a political transition that sidelined Syria's president.
Largely symbolic - by BBC defence correspondent Jonathan Marcus
France looks to be moving towards airstrikes in Syria, as well as those it has already launched in Iraq.
Britain is in a broadly similar position, with senior government figures talking about the need to consider extending strike missions to Syria - though in Britain such a step would require parliamentary approval.
Australia too is weighing up Syrian strikes. The number of additional strike sorties though would be small.
Britain, for example, is already flying a pair of Tornados each day and there appear to be no plans to expand the number of aircraft involved if the scope of the mission broadens.
This is therefore to a large extent symbolic; encouraged in part by the need to be seen to respond to the refugee crisis emanating from Syria.
Experts say the West and its Arab allies still lack a coherent policy for tackling Syria's myriad problems.
IS extremists have made significant gains on the ground in Syria as one of the groups in the uprising against President Assad, and have also been fighting other rebels. They have also captured large areas of Iraq.
A US-led coalition is carrying out airstrikes in Syria and Iraq, but France had limited its planes to Iraqi airspace until now.
A Russian foreign ministry spokeswoman said on Monday it was "premature" to say Russia was involved in the fighting in Syria, although it was no secret Moscow had been supplying Damascus with equipment to fight "terrorists".
The US, which strongly opposes President Assad, has expressed concern at reports of an imminent Russian military build-up aimed at assisting his government.
Syrians fleeing the conflict make up the majority of the thousands arriving in Europe looking for asylum.
Speaking at the Elysee Palace on Monday, Mr Hollande said his country would take in 24,000 refugees.
UK Prime Minister David Cameron was due to set out details later of his government's plans to resettle more refugees from Syria, as well as any further military action.