The head of MI5 has warned that Islamic State aspires to commit “devastating” and “more complex” attacks in Europe after losing territory in the Middle East.

Andrew Parker told European security chiefs in Berlin the group required international focus “for years”. He revealed 12 terror attacks have been stopped in the UK since the Westminster attack in 2017. He condemned Russia for the “reckless” poisoning of the Skripals in Salisbury.

Mr Parker warned the threat posed by IS, which he referred to as Daesh, would persist, driven by its “murderous ideology”. “Whilst Daesh has now lost its false caliphate in its strongholds in Syria and Iraq, tackling the group as a movement will require sustained international focus for years to come,” he said. “As I speak today, they are seeking to regroup, and the threat seems likely to persist.”

Security and intelligence expert Phil Ingram said that there is competition between different extremist groups. “Islamic State have been blamed for [attacks] – that’s upset a lot of al-Qaeda-affiliated groups who want to get back into high-level, sophisticated attacks like they did with the 9/11 attacks, because they see Islamic State getting the media limelight,” he said.

Mr Parker also accused the Kremlin of “flagrant breaches of international rules” over the Salisbury poisoning attack in March. Russian ex-spy Sergei Skripal and his daughter Yulia were exposed to a nerve agent belonging to the Novichok group.

The Russian government has denied any involvement, but has been the subject of condemnation and diplomatic sanctions from the West.

Mr Parker said: “The reckless attempted assassination of Sergei Skripal, using a highly lethal nerve agent, put numerous lives at risk, including that of his daughter. “It was only through near-miraculous medical intervention that his and his daughter’s lives were saved, and wider preventive action was able to be taken.”

Mr Parker described the attempted assassination of the Skripals as a “deliberate and targeted malign activity” which risked Russia becoming a “more isolated pariah”. He condemned Moscow by calling for the need to “shine a light through the fog of lies… out of their propaganda machine”. “One of the Kremlin’s central and entirely admirable aims is to build Russian greatness on the world stage,” he said. “But its repeated choices have been to pursue that aim through aggressive and pernicious actions by its military and intelligence services.”

Mr Parker’s speech comes after one person was killed and four others were injured by a knifeman in Paris on Saturday. The attack was claimed by IS.

In December last year, Mr Parker reported that nine terrorist attacks had been prevented by the security services and police in 2017.

Monday’s updated total brings the number of disrupted attacks in the UK to 25 since 2013.

In his speech, the chief of the security service said he was “confident about our ability to tackle these threats, because of the strength and resilience of our democratic systems, the resilience of our societies and the values we share with our European partners”. Mr Parker added that European intelligence agencies must rely on “shared co-operation more than ever”. And he thanked European security services for their support in the investigation into the Manchester bombing last year. “European intelligence cooperation today is simply unrecognisable to what it looked like five years ago.”