The Israeli embassy in London was reportedly the target of a terror plot linked to Iran that was thwarted “with hours to spare”.
Five Iranian nationals were among eight men arrested in two separate counter-terrorism investigations on Saturday.
Counter-terrorism officers, supported by the military, swooped in to make arrests fearing an attack was imminent.
They were allegedly planning an atrocity at the embassy in Kensington, the Times reported on Wednesday.
Iran’s foreign minister “categorically” denied reports linking Iranian nationals to an alleged terrorist scheme targeting the Israeli embassy.
In a post on X, Iranian foreign minister Seyed Abbas Araghchi rejected reports of Iranian citizens’ involvement.
“Iran in no uncertain terms categorically rejects any involvement in such actions and confirms that we have not been informed of any allegations via proper diplomatic channels,” he said.
“Iran has urged the UK to engage so that we may assist any probe into credible allegations. Timing and lack of engagement suggest that something is amiss.”
Mr Araghchi said there had been a “history of third parties bent on derailing diplomacy” and “provoking escalation resorting to desperate measures, including false flag operations”.
“Iran stands ready to engage to shed light on what has truly transpired, and we reiterate that UK authorities should afford our citizens due process,” he said.
“As soon as possible we will look to share further details and in the meantime we would ask the public to remain vigilant and contact us if you have any concerns.”
The Israeli embassy has been approached for comment.
The Metropolitan Police has not confirmed the target of the alleged plot and said speculation “could have a negative impact as we work to keep the public safe from potential threats”.
Yvette Cooper, the home secretary, called it one of the biggest counter-terrorism operations in recent years.
Security Minister Dan Jarvis in an update on Tuesday the two operations that took place on Saturday were against some of the "largest counter state threats....we have seen in recent times".
In a statement to MPs, he said it would not be appropriate for the Government to "speculate on or comment further" on the motivations behind the cases that led to the arrests.
The minister also refused to give details on the immigration status of the suspects when pressed by several MPs.
"There are very strict limitations on what ministers can say at this point because it would be unforgivable, frankly, to cut across live counter terrorism," he said.
Seven of the men arrested remain in police custody and one suspect was bailed on strict conditions.
In one operation, three men were arrested at separate addresses in north-west London and west London under the National Security Act 2023, which focuses on state threats.
Mr Jarvis said: "I can confirm to the House that these are the first Iranian nationals arrested under the National Security Act."
He added: "The operations to execute these eight arrests under both counter-terror and counter -state threat powers, in different parts of the country, in the space of 24 hours were intensive."
In the second operation, five men - all Iranian nationals - were arrested on suspicion of preparing an act of terrorism at locations across England on Saturday after a suspected plot to target a single premises was uncovered by counter-terror police.
Officers carried out searches at addresses in Greater Manchester, London and Swindon areas, while searches are continuing at multiple locations across the country, Mr Jarvis said.
He said what follows is "careful, painstaking work" in an incredibly complex set of investigations.
He added: "The House will be aware that these operations come against a backdrop of complex, interconnected threats to the UK - where state threats and counter-terrorism, as well as serious and organised crime, are intertwined together."
Iran was the first foreign power to be listed on the top level of the foreign influence registration scheme (Firs) earlier this year, aimed at protecting the UK from malign foreign influence.
It means anyone who is directed by the regime to carry out activities in the UK must declare it or face five years in prison once the scheme comes into force in July.
Announcing the move in March, Mr Jarvis said the Islamic Republic of Iran had become "increasingly emboldened, asserting itself more aggressively to advance their objectives and undermine ours".
In October last year, the head of MI5, Ken McCallum, said that authorities had stopped 20 state-backed plots hatched by Iran in the UK since 2022.
On Tuesday, shadow home office minister Matt Vickers said the two separate arrests of Iranian nationals "raise serious questions about how their networks were formed and what their intentions were", and urged the Government to unveil the immigration status of those arrested.

The Government has also faced pressure to designate Iran's Islamic Revolutionary Guard Corps (IRGC), a terrorist organisation.
Liberal Democrat home affairs spokeswoman Lisa Smart asked ministers whether the Government will carry out an audit into Iran-linked assets in the UK, telling the Commons "consecutive governments are yet to proscribe the Iranian Revolutionary Guard Corps as a terrorist organisation".
She urged ministers to "look closely" at whether sanctioned individuals linked to the Iranian regime have assets in the UK.
Mr Jarvis said: "We take these matters incredibly seriously."
Commander Dominic Murphy, Head of the Met’s Counter Terrorism Command said: "Any speculation around this investigation could have a negative impact as we work to keep the public safe from potential threats.
“This is a fast-moving counter-terrorism investigation and there are significant operational reasons why we cannot provide further information at this time. As soon as possible we will look to share further details and in the meantime we would ask the public to remain vigilant and contact us if you have any concerns."