Russia’s intelligence agency has been on a mission to generate “sustained mayhem on British and European streets”, the head of MI5 has said.

Giving his annual update on security threats faced by the UK, Ken McCallum said GRU agents had carried out “arson, sabotage and more dangerous actions conducted with increasing recklessness” in Britain after the UK backed Ukraine in its war with Russia.

MI5 had also responded to 20 plots backed by Iran since 2022, he said, although he added the majority of its work still mostly involved Islamist extremism followed by extreme right-wing terrorism.