Britain's government Monday accused Iran's Revolutionary Guards of being behind a major scare at a UK airbase used by the United States, as allies including Washington warned Tehran against hostile acts.
Iran denied any involvement.
UK Prime Minister Andy Burnham told the British parliament that Iran's Revolutionary Guard Corps (IRGC) "almost certainly directed" an incident at the Royal Air Force base of Fairford in southwest England last month.
The US, which had been using the base for its war in Iran, abruptly withdrew all its B-1 bombers from the site last week after the mysterious episode on September 27.
Burnham said Britain's assessment of the incident was that it "is highly likely to have been coordinated in Iran, almost certainly directed by Iran's Revolutionary Guard".
"We will not tolerate these threats on our soil. We will crack down on Iran's use of criminal networks, using our full range of powers to target them and their funding streams," he told MPs.
Iran's state news agency IRNA reported that "the Iranian ambassador in London, Ali Moussavi, has again categorically rejected the accusations concerning Tehran's role in the incident at the Fairford military base" and "called on the British government to present evidence supporting its allegations if it possesses any."
Shortly after Burnham spoke to parliament, 29 countries, including the US, Britain, Australia, Canada, France and Germany, released a joint statement denouncing "in the strongest terms Iran's use of violent attacks".
The statement said such attacks included "acts of lethal plotting, arson, sabotage, cyber-attacks, and other hybrid activities against us and our partners".
"Any attempt by Iran to threaten, silence, intimidate, harass, harm, or coerce people on our territories through proxies or any other means is unacceptable," it read.
The Foreign Office confirmed in its own statement Monday that Iran's ambassador to the UK had been summoned for talks.
"We are also announcing the designation of two Iranian nationals for their role in facilitating or engaging in hostile activity on behalf of the Iranian regime, with the clear intent of threatening, planning or conducting attacks overseas," foreign minister Ed Miliband said.
The foreign ministry said the individuals included Ruhollah Bazghandi, the IRGC's head of counterespionage operations, who is "now subject to an immediate asset freeze, travel ban and director disqualification".
Speculation has swirled about the incident since police were called to the base after a local farmer reported a group of men with several white vans engaged in "suspicious" activity.
- 'Major' incident -
Despite a major counter-terrorism probe, seven suspects arrested in the days following, including a British-Iranian national, have all since been released on bail. None has been charged.
The incident was declared "major" by British authorities and triggered the evacuation of a nearby village.
But the source and nature of the threat have remained shrouded in mystery.
Investigators did not find any explosives in the vans, but did recover some petrol, according to officials.
Burnham has previously said there were "strong indications that Iran played a part" in the incident, which Tehran has rejected.
Britain gave Washington permission in March to use Fairford for "specific defensive operations into Iran," and US bombers and other planes had been seen taking off and landing at the base.
US President Donald Trump has said Washington withdrew its bombers because of "threats" he believed were linked to Tehran.
In the foreign ministry statement, Miliband noted that the UK had already "designated the IRGC under our new state threats powers, and imposed major sanctions on those responsible for Iran's malign activity".
