Israel attacked an Iranian TV station in an air raid on Tehran in the early hours of Tuesday.
The state-owned Islamic Republic of Iran Broadcasting said it was hit by two explosions. Israel acknowledged the strike, calling it an attack on Iranian "propaganda activities".
Missile sirens sounded in Israel, and explosions were heard in the Gulf as the regional conflict entered a fourth day. Iran had warned on Monday it was ready for a "long war".
The Iranian TV channel said it was still broadcasting after the strike, reporting no casualties. The Israeli army had ordered local residents to leave the Evin area of Tehran, which is also home to a notorious regime prison.
But most Iranians cannot see such warnings, which are published on social media, because the internet is largely down across the country.
Israel said the complex attacked was a "communications centre" for the Islamic Revolutionary Guard Corps. It described the state broadcaster as the "beating heart of the IRGC's machine of lies and repression".
Fars news agency, which is affiliated to the Guards, said the area around Iran’s former parliament building was also attacked by US and Israeli air strikes. The police have a building near by, it said.
Other Israeli eviction orders were issued in several areas of Lebanon, including near the offices of Hezbollah-affiliated TV channel Al Manar.
Iran had indicated on Monday it is ready for a long conflict. Iranian state media reported on wartime measures being implemented by the state, including increasing medicine stocks and the readiness of hospitals, and ensuring reliable energy production and fuel supply to residents.
Ali Larijani, secretary of the Supreme National Security Council and adviser to late supreme leader Ayatollah Ali Khamenei, ruled out negotiations as Israel continued its military campaign.
"Trump's wishful thinking has dragged the whole region into an unnecessary war, and now he is rightly worried about more American casualties," Mr Larijani said.
But Iran, "unlike the US, prepared itself for a long war … regardless of the costs and will make the enemies sorry for their miscalculation", he said in another post.
Six US troops have been killed in the campaign against Iran, it was revealed on Monday. Defence Secretary Pete Hegseth said the US is hitting Iran “certainly, overwhelmingly and unapologetically" but that the war on the regime is "not endless".
“To the media outlets and political left screaming ‘endless wars’, stop. This is not Iraq. This is not endless,” he said in his first public address since the onset of the war. “We fight to win and we don’t waste time.”
Mr Larijani denied claims by Mr Trump that Iran’s interim leadership is willing to resume talks. Calls for dialogue and calm have gone unanswered, as US, Israeli and Iranian forces continued to exchange fire on Monday.
The Israeli army said its air force began an "additional broad strike" on Iranian targets in the heart of Tehran. At least 555 people have been killed in the attacks across Iran since Saturday, the country's Red Crescent Society said.
The US-Israel strikes have killed senior military commanders, as well as civilians. Iran says at least 165 children were killed in an attack on a school in the southern Minab province. Iran's Foreign Minister Abbas Araghchi sent a letter to UN Secretary-General Antonio Guterres alleging "war crimes and crimes against humanity committed by the US and the Israeli regime".
"Numerous military attacks have been carried out against civilian targets, including schools, hospitals, equipment and aid workers," wrote Mr Araghchi. "This series of widespread and systematic attacks against the civilian population fully places these actions within the definition of crimes against humanity."
Brig Gen Majid ibn Reza has been appointed as Iran's acting Defence Minister, state media said. He replaces Amir Nasirzadeh, who was among the senior military commanders killed on the first day of US-Israeli attacks.
Regional spillover
Israeli overnight air strikes on Beirut’s southern suburbs and southern Lebanon killed at least 31 people and wounded 149, according to a preliminary toll issued by Lebanon’s Health Ministry on Monday.
The deadly attacks came after Hezbollah claimed responsibility for firing rockets into Israel overnight to avenge the death of Mr Khamenei, prompting a wide-reaching retaliation. The Hezbollah attack was the first on Israel since a ceasefire came into place, despite near-daily Israeli strikes on Lebanon.
The Israeli army launched a second wave of strikes across what it says are Hezbollah targets across Lebanon on Monday, warning that the group will pay a heavy price for its attack and the group's leader, Naim Qassem, is "now a marked target for assassination".
Iranian attacks on its Gulf neighbours also continued on Monday.
Iranian drones struck a power plant and a site belonging to oil and gas company QatarEnergy, with no casualties reported, said the Qatari Defence Ministry.
Qatar also intercepted Iranian attacks on the country's international airport, the Qatari Foreign Ministry spokesman said, adding that attacks could not remain unanswered.
Meanwhile, Saudi Aramco shut down operations at its Ras Tanura refinery after a fire broke out following a reported drone attack in the first Iranian strike on the Gulf’s energy infrastructure.
Iran’s deputy foreign minister has denied that Tehran was behind the reported bombing of Saudi oil facilities, amid rising regional tensions.
“We are not responsible for the bombing of Saudi oil fields and we have informed our brothers in the Kingdom of this,” he told CNN.
Members of the Gulf Co-operation Council said they will take "all necessary measures" to defend their security and territory, reserving the right to respond to what they described as "heinous" and "treacherous Iranian attacks" in a joint statement.
Meanwhile, the US, Bahrain, Jordan, Kuwait, Qatar, Saudi Arabia and the UAE issued a joint statement in which they strongly condemned Iran's "indiscriminate and reckless missile and drone attacks". Gulf states had previously said they would not allow their territory to be used for attacks against Iran.
