Warplanes based in Iraq and Syria had been deployed to intercept airborne strikes after Tehran announced it had launched an assault on Saturday.

The Prime Minister was to join other G7 leaders on a call on Sunday amid fears of further escalation in the event of a possible Israeli counter-strike.

Speaking to journalists in Downing Street, Mr Sunak said if Iran’s attack on Israel been successful “the fallout for regional stability would be hard to overstate”, as he confirmed RAF pilots shot down “a number of” drones.

Israel said Iran launched 170 drones, more than 30 cruise missiles and at least 120 ballistic missiles early on Sunday in an attack that set off air raid sirens across the country.

The assault was launched in response to a strike widely blamed on Israel on an Iranian consular building in Syria earlier this month which killed two Iranian generals.

It marks the first time a direct military assault has been launched by Tehran on Israel despite enmity dating back to the country’s 1979 Islamic Revolution.

The development threatens to become a major regional escalation after years of shadow wars fought between the two foes as the war in Gaza inflames decades-old tensions in the Middle East.

Britain and the US have offered staunch support for Israel, although Tehran has threatened a “heavier” response if Washington cooperates in any further military action.

Israeli military spokesman rear admiral Daniel Hagari said 99% of more than 300 drones, cruise missiles and ballistic missiles had been shot down outside the country’s borders, with aircraft intercepting more than 10 cruise missiles.