Isis jihadists are planning “large scale” terror attacks and focussing primarily on European targets, Europol has said.

The police agency launched a new Europe-wide counter-terror intiative on Monday, and warned that the threat from Isis was the worst the continent has faced in more than 10 years.

Rob Wainwright, the director of Europol, said militants had developed a new combat strategy to attack major European cities, and the agency also cited the growing number of Isis foreign fighters as a “posing new challenges for EU members states”.

But amid growing attempts to link such challenges to the intake of more than one million refugees into Europe last year, the police agency said in a report that there was “no concrete evidence” to suggest this was the case.

Releasing the findings of an expert review into the Paris shootings of 13 November, Europol said it had found nothing to suggest “that terrorist travellers systematically use the flow of refugees to enter Europe unnoticed”.

Rather, it warned of the risk to Europe if those who do arrive are turned away from their adopted countries into the hands of jihadist recruiters.

The agency said: “It is possible that elements of the (Sunni Muslim) Syrian refugee diaspora in Europe may be vulnerable to radicalisation. Indeed there are reports that refugee centres are being specifically targeted by Islamic extremist recruiters.”

At a press conference in Amsterdam on Monday, Europol launched the European Counter Terrorism Centre (ECTC), and said that its review of the Paris shootings revealed the importance of EU members sharing intelligence.

“Our ambition is for the European Counter Terrorism Centre to become a central information hub in the fight against terrorism in the EU, providing analysis for ongoing investigations and contributing to a coordinated reaction in the event of major terrorist attacks,” Mr Wainwright said.

Europol said that, after the Paris attacks, there is “every reason to expect that Isis will undertake a terrorist attack somewhere in Europe again… intended to cause mass casualties amongst the civilian population”.

“Intelligence suggests Isis has developed an external action command trained for special forces style attacks in the international environment,” it added. Ard van der Steur, the Dutch justice minister, said at the launch of the ECTC that it will “improve the exchange of information between law enforcement agencies”.