Iran's Supreme Leader Ayatollah Ali Khamenei hit back on Wednesday at Donald Trump's call for his country to surrender.
He warned that any US air strikes on Iran would have "serious irreparable consequences".
Britain stressed that the Middle East has been plunged into an “incredibly dangerous moment” as Israel hit Tehran with more air strikes and Trump was said to be considering whether to order US attacks on Iran.
Israel said more than 50 fighter jets took part in the morning strikes and claimed to have hit a centrifuge manufacturing facility in Tehran.
Residents of Tehran fled their homes in droves on the sixth day of Israel’s air campaign aimed at Iran’s military and nuclear programme - which a human rights group says has killed at least 585 people across Iran and wounded 1,326 others.

Iran has retaliated against Israel’s airstrike campaign by launching some 400 missiles and hundreds of drones at Israel. So far, 24 people have been killed in Israel.
UK government minister Matthew Pennycook said: “This is obviously an incredibly concerning and dangerous moment for the entire region.
“Further escalation is in no-one’s interests. We continue to urge both sides to show restraint.”
A major explosion could be heard around 5am in Tehran on Wednesday morning, following other explosions that boomed earlier in the predawn darkness.
Authorities in Iran offered no acknowledgement of the attacks, which has become increasingly common as the Israeli airstrike campaign has intensified since it began on Friday.
At least one strike appeared to target Tehran’s eastern neighborhood of Hakimiyeh, where the paramilitary Revolutionary Guard has an academy.
Traffic stood bumper to bumper on roads to the west and central Tehran emptied out, with many shops shuttered as well as the ancient Grand Bazaar. The Bazaar has closed only in times of crisis, such as during the 2022 anti-government protests and the coronavirus pandemic.
Israel has also claimed that it had killed Gen. Ali Shadmani, whom it described as Iran’s most senior remaining military commander.
Shadmani was little known in the country before being appointed last week to a chief-of-staff-like role as head of the paramilitary Revolutionary Guard’s Khatam al-Anbiya Central Headquarters following the killing of his predecessor, Gen. Gholam Ali Rashid, in an Israeli strike.
Israel asserts it had to launch its airstrike campaign to stop Iran from getting closer to being able to build a nuclear weapon.
The US president is reportedly considering if the US should join Israeli strikes on Iran.

Trump is weighing a range of options, including a possible strike, following a meeting with his national security team inside the Situation Room, NBC News reported, citing unnamed officials.
America sent more warplanes to the Middle East as Trump made a series of statements about the conflict that fuelled confusion about the US’s role, including demanding “UNCONDITIONAL SURRENDER” in a post on social media.
He also warned Supreme Leader Ayatollah Ali Khamenei that the US knows where he is hiding but that there were no plans to kill him “at least not for now.”
Trump and Israel’s Prime Minister Benjamin Netanyahu spoke about the evolving situation over the phone on Tuesday, according to a White House official.
Iran offered no immediate response to the president’s posts, but the country’s military leaders vowed that Israel would soon see more attacks.
“The operations carried out so far have been solely for the purpose of warning and deterrence,” Gen. Abdul Rahim Mousavi, the commander in chief of Iran’s army, said in a video. “The punishment operation will be carried out soon.”

Israel’s military warned the population to stay close to shelters as Iran fired new salvos of missiles on Wednesday, but officials said most were intercepted and Israel’s rescue services had no immediate reports of injuries. Sirens blared in southern Israel, including in the desert town of Dimona, the heart of Israel’s never-acknowledged nuclear arms programme.
The US State Department announced that the US Embassy in Jerusalem will remain closed through Friday.
Iran has fired fewer missiles in each of its barrages, with just a handful launched into Wednesday. It has not explained the drop in missiles fired, but the decline comes after Israel targeted many Iranian launchers.