British Prime Minister Andy Burnham said Monday that Iran was “highly likely” to have been behind the thwarted attack on RAF Fairford and that the IRGC was almost certainly involved.

The military base in southwest England was used by the United States to launch attacks on Iran and became the site of a security response after five men were arrested there on Sept. 27 for suspected offenses related to terrorism and explosive activities. Two more men were subsequently arrested, and all were released on bail with restrictions.

U.S. officials told Reuters that there had been suspicion of an Iranian plot to launch a drone attack, and the U.S. withdrew its bombers as a precaution, according to President Donald Trump.

“I can confirm our assessment that it is highly likely to have been coordinated in Iran, almost certainly directed by Iran’s Islamic Revolutionary Guard (IRGC),” Burnham told Parliament.

“We will not tolerate these threats on our soil,” Burnham said. “We will crack down on Iran’s use of criminal networks, using our full range of powers to target them and their funding streams, and we will bring further sanctions to restrict the capacity of Iran and the IRGC to do us harm.”

The Iranian regime pushed back on the accusation, calling it “unfounded and malicious ​speculations.”

The foreign ministries of the U.S. and 28 other countries, including the U.K., Canada, France, and Germany, issued a joint statement denouncing “Iran’s use of violent attacks, including the acts of lethal plotting, arson, sabotage, cyberattacks, and other hybrid activities against us and our partners.”

“The UK has also concluded this event demonstrates the IRGC’s continued willingness to project hostile activity beyond its borders through covert networks and proxy actors,” the statement said, adding that the RAF Fairford incident follows a “campaign of attacks across Europe targeting Jewish communities, Iranian journalists, and US interests.”

Any Iranian effort to “threaten, silence, intimidate, harass, harm, or coerce people on our territories through proxies or any other means is unacceptable,” the statement added.

The Iranian regime “should be in no doubt that we are united and remain committed to safeguarding our sovereignty and strengthening our international coordination, bolstering our national resilience, protecting our communities, and ensuring that those responsible are held to account,” the countries declared.