Sir Keir, who was on the phone to the Israeli PM when the assault was launched, said the rockets were aimed at civilian targets and it is “too soon to assess the impact fully”.
“I utterly condemn this attempt by the Iranian regime to harm innocent Israelis, to escalate this incredibly dangerous situation and push the region ever closer to the brink,” he said.
“We stand with Israel and we recognise her right to self-defence in the face of this aggression.”
Sir Keir called on Iran to “stop these attacks”, saying it had “menaced the Middle East for far too long”.
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“I am deeply concerned that the region is on the brink, and I’m deeply concerned about the risk of miscalculation,” he added.
Asked if the UK would be prepared to use British military capabilities to help Israel defend itself against Iran, which backs the militant group, the prime minister said: “This, as you’ll appreciate, is an evolving situation.
“But what I will say is that we stand with Israel and her right to self-defence. And any relevant updates will be provided in due course.”
Sir Keir also chaired a ministerial meeting in Downing Street on Tuesday on the situation in the Middle East.
The attack on Israel began while he was talking to the country’s Prime Minister Benjamin Netanyahu, Number 10 revealed earlier this evening.
Sir Keir would not go into details of the call, but said all his discussions with world leaders on the conflict focus on the need for a ceasefire and a political solution.
“My calls have been about the importance of creating the space and the conditions for that de-escalation, and to find that political route forward,” he told reporters after his televised address.
He added that with Mr Netanyahu he was able to “make the case for a ceasefire in Gaza”, which has been under seige for the past year following the Hamas attrocitie
The prime minister also repeated the advice for Britons in Lebanon to leave immediately, saying “we’re doing everything we can to get people out, but the situation is extremely volatile”.
“If you have the means to leave, the time is now,” he said.
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Speakers at the Bitcoin Amsterdam 2024 conference discussed how flawed academic studies on Bitcoin fuel misinformation, affect media coverage and lead to misguided policies.