Prime Minister Sir Keir Starmer has urged de-escalation following Israeli strikes targeting nuclear and military sites in Iran.

He spoke to Israeli Prime Minister Benjamin Netanyahu on Friday afternoon and shared the UK’s “grave concerns” about Iran’s nuclear programme, No 10 said, as a fresh wave of Israeli strikes targeting Tehran began.

Fears of a full-scale conflict have been stoked by warnings of “severe punishment” from Iran’s Supreme Leader Ayatollah Ali Khamenei and reports of drone launches in response.

A Cobra emergency meeting was held earlier to discuss the UK response to the situation.

In a social media post, Sir Keir said he had been “engaging partners to de-escalate,” calling for “restraint, calm and a return to diplomacy”.

On his call to Netanyahu, a No 10 spokesman said: “The Prime Minister was clear that Israel has a right to self-defence and set out the UK’s grave concerns about Iran’s nuclear programme.

“He reiterated the need for de-escalation and a diplomatic resolution, in the interests of stability in the region.”

Sir Keir also spoke to French President Emmanuel Macron and German Chancellor Friedrich Merz on Friday morning and made a joint call for diplomacy.

A Downing Street spokesman said: “The leaders discussed the long-held grave concerns about Iran’s nuclear programme, and called on all sides to refrain from further escalation that could further destabilize the region.”

Asked if the UK is involved in nuclear talks with US and Iran, he said: “On Iran’s nuclear programme, it is more advanced than ever, and it is a clear threat to international peace and security.

“We’ve urged Iran to continue engaging with President Trump’s offer of a negotiated solution and we continue to liaise closely with our partners on this.

“We remain committed to finding a diplomatic solution but are prepared to take every diplomatic step to prevent Iran from developing nuclear weapons, including through snapback, if necessary.”

The UN snapback mechanism would lead to the re-imposition of international sanctions against Iran developing nuclear weapons, which had been lifted in 2015.

Foreign Secretary David Lammy had cancelled a planned trip to Washington DC to meet his counterpart Marco Rubio, and instead spoke to his equivalent in Iran, in what he said was a “moment of grave peril in the Middle East”.

In a meeting with journalists, Lammy was asked several times about whether the UK had been informed before Israel made its strikes against Iran overnight. He said the UK was “not involved” and emphasised that Israel took “unilateral action”.

UK officials said the UK did not play any part in the action overnight but is continuing to monitor the situation.

Conservative leader Kemi Badenoch declined to condemn Israel’s actions, stressing “Iran is an enemy of the UK” that had attempted terrorist acts “on UK soil”.

She added: “If Israel is stopping Iran from getting nuclear weapons they should not be condemned for that.”

Badenoch added the UK should be increasing defence spending as well as energy security.

Rubio also said that Israel acted unilaterally, adding in a post on X that the US is “not involved in strikes against Iran and our top priority is protecting American forces in the region”.

The attack appeared to be the most significant Iran has faced since its war with Iraq in the 1980s.

Israeli Prime Minister Benjamin Netanyahu said that Israel had “struck at the heart of Iran’s nuclear enrichment programme” and “the heart of Iran’s nuclear weaponisation programme”.

Netanyahu added the “operation will continue for as many days as it takes to remove this threat”.

Iranian state television reported that the leader of the paramilitary Revolutionary Guard Hossein Salami was killed as well as chief of staff of the Iranian armed forces, General Mohammad Bagheri.

Liberal Democrat leader Sir Ed Davey said international leadership was needed from the UK government.

“People across the UK and the world will be fearing the break-out of widespread regional conflict in the Middle East, following Israel’s strikes overnight,” he said.

“The UK must work with allies to contain Iran’s nuclear ambitions through diplomacy, not war.”