The UK’s domestic spy chief warns that Iran is ramping up attempts to hit harder targets, such as military sites, in the United Kingdom, after Prime Minister Andy Burnham said Iran played a role in a recent incident at the RAF Fairford airbase, Al Jazeera reports.

In his annual speech on ranging threats to the UK, MI5 Director General Ken McCallum says that while he cannot speak about the Fairford incident because of an ongoing investigation, he says a major shift this year in “Iranian ambitions to come at harder targets, like military sites” has been observed.

“The RAF Fairford incident … is not unique. There have been other examples, not just in the UK but around the world,” he says.