UK Prime Minister Rishi Sunak called Sunday for "calm heads to prevail" as he confirmed that British fighter jets had shot down Iranian drones during Tehran's unprecedented attack on Israel.

Israel and its allies intercepted almost all of the missiles and drones fired by Iran during its first-ever attack on Israeli territory.

Sunak joined world leaders in urging restraint as Iranian President Ebrahim Raisi warned against any "reckless" Israeli retaliation to the strikes, which marked a major escalation in Middle East tensions.

"If this attack had been successful, the fallout for regional stability would be hard to overstate," Sunak told reporters in Downing Street.

"We stand by the security of Israel and the wider region, which is of course important for our security here at home, and what we now need is for calm heads to prevail.

"We'll be working with our allies to de-escalate the situation and I look forward to speaking to G7 leaders later this afternoon," Sunak added.

He also said that British Royal Air Force planes "did shoot down several Iranian attack drones," confirming reports that Britain had helped Israel and other allies repel the strikes.

Defence Minister Grant Shapps said UK warplanes had "intercepted and destroyed multiple one-way attack drones launched by Iran and its proxies".

He said on social media site X that the drones had "posed a threat to civilian lives" and that all British aircraft "returned safely to base".

The defence ministry had said late Saturday that it had sent additional fighter jets and air refueling tankers to the Middle East in the face of the Iranian threats to Israel.

The planes bolstered an existing British operation in Iraq and Syria against the Islamic State group, the Ministry of Defence added.