Britain is facing a “staggering rise” in assassination attempts on UK soil by Russia and Iran, as the hostile states recruit criminals to “do their dirty work” for them, the head of the UK’s domestic intelligence agency said Tuesday.

MI5 director Ken McCallum said his agents and police have tackled 20 Tehran-backed plots since 2022 and warned that Iran could expand its targets in the UK if Israel attacks in response to Iran’s missile barrage. The spy chief said the widening conflicts in the Middle East raise the risk “of an increase in – or broadening of – Iranian state aggression in the U.K.” In a rare public speech setting out the major threats to the UK from both hostile states and terror groups, McCallum said there also is a risk that Israel’s conflicts with Iran-backed militant groups — Hamas in Gaza, Hezbollah in Lebanon and the Houthis in Yemen - could trigger terror attacks in the UK.

The Middle East crisis has not translated “at scale into terrorist violence” in Britain, he said, but hostile states, individual attackers and a revived Islamic State group combine to create “the most complex and interconnected threat environment we’ve ever seen.”

The number of state-threat investigations undertaken by MI5 has risen by 48% in the past year, with Iran, Russia and, China the main perpetrators, McCallum told journalists at the UK’s counterterrorism command center in London.

McCallum said that since the death of Mahsa Amini, who died in Iranian police custody in September 2022 after being detained for allegedly violating the Islamic republic’s mandatory headscarf law, “we’ve seen plot after plot here in the UK, at an unprecedented pace and scale.”

He said MI5 and the police have responded to 20 potentially lethal Iran-backed plots since January 2022, an increase of a third on the figure of 15 the government gave at the end of January.

McCallum said Russia’s military intelligence agency was trying to use “arson, sabotage and more” to create “mayhem” on the streets of Britain and other European countries.

Both Russia and Iran often turn to criminals, “from international drug traffickers to low-level crooks,” to carry out attacks, he said,

The UK’s official terror threat level stands at “substantial,” the middle of a five-point scale, meaning an attack is likely, and since 2017 MI5 and the police have disrupted 43 late-stage terror plots.

While about three-quarters of terror plots stem from Islamic extremist ideology and a quarter from the extreme right, he said those labels “don’t fully reflect the dizzying range of beliefs and ideologies we see,” drawn from a soup of “online hatred, conspiracy theories and disinformation,” McCallum said.

He also said there was worrying signs that the Islamic State group is back, despite the collapse of its self-declared caliphate in Iraq and Syria.

McCallum said that “after a few years of being pinned well back, they’ve resumed efforts to export terrorism.”

“The first 20 years of my career here were crammed full of terrorist threats,” McCallum said. “We now face those alongside state-backed assassination and sabotage plots, against the backdrop of a major European land war.”