Sir Keir Starmer has called on Israel and Iran to “step back” from the brink of all-out war.

The Israeli air force attacked Tehran’s nuclear facilities and assassinated the head of the Iranian armed forces, General Mohammed Bagheri.

Nuclear scientists and the head of the Islamic Revolutionary Guard Corps, Hossein Salami, were also slain in the military operation involving 200 fighter jets.

In response, Iran launched more than 100 drones, Israel’s military said.

Israel is braced for a further retaliatory attack which Tehran said would be “harsh and decisive”.

But Prime Minister Sir Keir Starmer warned both countries “escalation serves no one in the region”.

He said: “The reports of these strikes are concerning and we urge all parties to step back and reduce tensions urgently. Escalation serves no one in the region.

“Stability in the Middle East must be the priority and we are engaging partners to de-escalate. Now is the time for restraint, calm and a return to diplomacy.”

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

Sir Keir’s sentiments were echoed by Foreign Secretary David Lammy, who said stability in the Middle East was “vital” for global security.

“Further escalation is a serious threat to peace & stability in the region and in no-one’s interest,” he said in a post on X.

“This is a dangerous moment & I urge all parties to show restraint.”

Iran’s Supreme Leader condemned the “evil and bloody” Israeli strikes this morning, saying that Tehran’s foe had revealed its “wicked nature” by hitting residential areas.

“The regime should await a harsh response,” Ali Khamenei said.

In a message to the nation, he said that several commanders and nuclear scientists were assassinated in the strikes, but that they would quickly be replaced.

“With this crime, the Zionist regime sealed for itself a bitter and painful destiny and will definitely see that [destiny] brought upon it,” he added.

Israeli fighter jets were still conducting strikes against Iranian military and nuclear facilities at 6am, according to its military.

“Our pilots attacked and are still attacking military targets and targets related to the nuclear programme in various areas in Iran,” military spokesman Brigadier General Effie Defrin told journalists.