MI5 Director General Sir Ken McCallum warned Tuesday that Iran has made a major shift this year toward targeting harder sites such as British military bases as part of an expanding hybrid campaign.

Speaking at the agency's Thames House headquarters in London, McCallum said operations linked to Iran had resulted in more than 50 arrests in the UK over the past year. He noted that much of the aggression has focused on Jewish communities and Israeli interests, with Tehran relying on criminal proxies.

The "major shift this year has been Iranian ambitions to come at harder targets, like military sites," McCallum stated. He described an incident near RAF Fairford in Gloucestershire as not unique, following Prime Minister Andy Burnham's assessment that it was almost certainly directed by Iran's Islamic Revolutionary Guard Corps.

McCallum placed Russia as "aggressor number one," accusing Moscow of escalating hybrid warfare below the NATO Article V threshold. State threats overall have quadrupled in the last decade, with MI5 now devoting more resources to them than during the Cold War, he said.

The warnings come amid heightened tensions, including recent US operations involving the airbase and broader concerns over sabotage and intimidation on British soil. McCallum expressed solidarity with targeted Jewish communities and stressed that those behind such actions would face an unflinching response.

Additional threats outlined included the misuse of artificial intelligence by terrorists and ongoing activities from other state actors, though Iran and Russia received particular emphasis in the hybrid domain.