David Cameron has offered François Hollande the use of Britain’s RAF airbase on Cyprus from which to launch airstrikes against Islamic State militants in Syria in the wake of the attacks on Paris.

Speaking alongside the French president at the Élysée Palace, Cameron said: “The United Kingdom will do all in its our power to support our friend and ally France to defeat this evil death cult.”

The prime minister signalled his determination to persuade parliament to back airstrikes against Isis targets in Syria. “We must also do more to defeat Isil in their heartlands in Syria and Iraq. Later this week in parliament I will set out our comprehensive strategy for tackling Isil. I firmly support the action President Hollande has taken to strike Isil in Syria and it is my firm conviction that Britain should do so too. Of course, that will be a decision for parliament to make.”

But Cameron offered practical help to France in its aerial campaign in Syria. “I have offered President Hollande the use of RAF Akrotiri for French aircraft engaged in counter-Isil operations and additional assistance for air-to-air refuelling,” he said.

As a major anti-terrorism operation continues in Belgium after the Paris attacks, Cameron called for more pan-European measures to tackle such threats.

“In particular, we must do more to tackle the threat of returning foreign fighters. This requires a pan-European effort.

“We must, without further delay, agree the rules to enable us to share passenger name records. It is frankly ridiculous we can get more information from countries outside the EU than we can from each other.”

Earlier, Cameron and Hollande visited the Bataclan concert hall, where scores of people were killed in the massacre by Isis gunmen.

The leaders viewed the floral tributes placed outside the music venue, where fans of rock group Eagles Of Death Metal were shot dead.

Cameron said the two men stood “shoulder to shoulder” and he paid tribute to the courage of the French people after the attack on their capital.

Belgian police have arrested 21 people since Sunday night in a major anti-terror operation, but the suspected Paris attacker Salah Abdeslam remained at large, a federal prosecutor said.

No arms or explosives were found in 24 raids across Brussels – including in the Molenbeek area from where the Paris attack was planned – they said.

Abdeslam was said by Le Soir newspaper to have been identified fleeing in the direction of Germany in a BMW. The federal prosecutor said in a statement that a BMW sighting near Liege that had been rumoured to contain Abdeslam had no links with the ongoing investigation.

The authorities urged a social media blackout of operations as the manhunt continued for surviving members of the group responsible for the deaths of 130 people in Paris.

Brussels remained on high alert on Monday over fears of a similar attack by Isis. Schools, universities and the metro system remained closed and some workers had been advised to stay at home while key suspects remained at large.

World leaders continued to consider how to respond to a string of recent attacks – including the bombing of a Russian plane over Egypt – with the UK moving nearer to joining allied airstrikes in Syria.

Cameron will present the case for increasing British military involvement to parliament later this week – with the Paris attacks and a unanimous UN security council resolution apparently galvanising support among MPs.

His talks with Hollande in Paris came as the French president started an intensive push to create a “grand coalition” to destroy Isis, which will take him to Washington and Moscow in the coming days. In between the two trips, Hollande is due to receive German chancellor Angela Merkel and Italy’s president Matteo Renzi.

A Commons vote on airstrikes could be held as early as next week, with George Osborne arguing that the Paris attacks and the UN resolution backing “all necessary measures” were swaying the argument.

“We’ll make the case as a government, we will allow MPs to digest that response and then we will see where we stand. Frankly, Britain has never been a country that stands on the sidelines and relies on others to defend us,” the chancellor said.

In the latest attacks, officials said five girl suicide bombers killed at least 12 people in Nigeria and Cameroon over weekend. Police blamed Boko Haram for the attacks, in which the bombers also died. The Guardian