David Cameron has vowed Britain will do "all in our power" to support France in its fight against Islamic State in the wake of the Paris terror attacks.

Following talks in the French capital with president Francois Hollande, the Prime Minister said he would set out his "comprehensive strategy" for dealing with IS in Parliament later this week.

"The United Kingdom will do all in our power to support our friend and ally France to defeat this evil death cult," he said.

Earlier the two leaders visited the Bataclan concert hall where scores of people were killed in the terrorist onslaught.

The two men discussed measures to improve intelligence-sharing and to work more closely with other Europe allies to counter the threat posed from jihadists returning after fighting in Syria and Iraq.

"This requires a pan-European effort. We need a stronger external EU border to protect our security more effectively," Mr Cameron said.

At the same time he said that more needs to be done to strike at IS - also referred to as Isil - in its heartlands of Syria and Iraq.

"I firmly support the action that President Hollande has taken to strike Isil in Syria and it is my firm conviction that Britain should do so too," he said.

He added: "It is clear that the world is coming together to tackle this evil terrorist threat. We have shown our firm resolve and together we will defeat this evil threat."

Mr Cameron said that he had offered the French air force the use of RAF Akrotiri on Cyprus to mount strikes on IS as well as RAF air-to-air refuelling support.

Mr Hollande also stressed the importance of hitting IS in Syria and said that French warplanes would be stepping up their attacks.

"This organisation is launching a war against us," he said.

"We will intensify our strikes, we will choose the targets that yield the best possible damage against the terrorist army," he said.

Earlier, the two leaders viewed the floral tributes placed outside the Bataclan music venue, where fans of rock group Eagles Of Death Metal were gunned down.

Meanwhile Belgian police arrested 16 people in a major anti-terror operation, but on-the-run Paris attacker Salah Abdeslam remains at large, a federal prosecutor has said.

No arms or explosives were found in 19 raids across Brussels - including the Molenbeek area from where the Paris attack was planned - or two in Charleroi, they said.

Abdeslam was said by Le Soir newspaper to have been identified fleeing in the direction of Germany in a BMW.

The authorities urged a social media blackout of operations as the desperate manhunt continued for surviving members of the group behind the gun and bomb murders of 130 people in the French capital.

Brussels remained on high alert over fears of a Paris-style IS attack.

Schools, universities and the underground system will remain closed and some workers have been advised to stay at home while key suspects remain at large.

As the search for the jihadists went on, world leaders were contemplating how to respond to a string of outrages - also including the downing of a Russian airline over Egypt - with the UK moving nearer to joining allied air strikes in Syria.

London Mayor Boris Johnson said that the city remained as safe as it was before the November 13 attacks in Paris, and said there was no need for school trips in the capital to be called off.

Responding to questions on Twitter, Mr Johnson said: "London is as safe as it was before the Paris attacks. School trips should go ahead."