The head of MI5 says Britain is facing a staggering rise in attempts at assassination, sabotage and other crimes backed by Russia and Iran.

Britain's domestic spy chief Ken McCallum warned of the dangers posed by Russia and Iran as well as growing concern about Al Qaeda and Daesh in his annual update on the threats faced by Britain on Tuesday.

The head of Britain’s domestic security service said Russia’s military intelligence service was pursuing “dangerous actions conducted with increasing recklessness.”