Israel launched an expanded assault on Iran on Sunday, targeting its energy industry and Defence Ministry headquarters, while Tehran unleashed a fresh barrage of deadly strikes.

The simultaneous attacks represented the latest burst of violence since a surprise offensive by Israel two days earlier aimed at decimating Tehran's rapidly advancing nuclear programme.

New explosions boomed across Tehran as Iranian missiles entered Israel's skies in attacks that Israeli emergency officials said caused deaths around the country, including four in an apartment building in the Galilee region. A strike in central Israel killed an 80-year-old woman, a 69-year-old woman and a 10-year-old boy, officials said.

Casualty figures weren't immediately available in Iran, where Israel targeted its Defence Ministry headquarters in Tehran as well as sites that it alleged were associated with the country's nuclear programme. Iran's paramilitary Revolutionary Guard claimed that Iranian missiles targeted fuel production facilities for Israeli fighter jets, something not acknowledged by Israel.

Amid the continued conflict, planned negotiations between Iran and the United States over Tehran's nuclear programme were cancelled, throwing into question when and how an end to the fighting could come.

“Tehran is burning," Israeli Defence Minister Israel Katz said on social media.

Both Israel's military and Iran state television announced the latest round of Iranian missiles as explosions were heard near midnight, while the Israeli security cabinet met.

Israel's ongoing strikes across Iran have left the country's surviving leadership with the difficult decision of whether to plunge deeper into conflict with Israel's more powerful forces or seek a diplomatic route.

Urgent calls to deescalate

World leaders made urgent calls to deescalate and avoid all-out war. The attack on nuclear sites set a “dangerous precedent,” China's foreign minister said. The region is already on edge as Israel makes a new push to eliminate the Iranian-backed militant group Hamas in Gaza after 20 months of fighting.

Israel — widely believed to be the only nuclear-armed state in the Middle East — said its hundreds of strikes on Iran over the past two days have killed a number of top generals, nine senior scientists and experts involved in Iran's nuclear programme. Iran's UN ambassador has said 78 people were killed and more than 320 wounded.

US intelligence agencies and the International Atomic Energy Agency have repeatedly said Iran was not pursuing a nuclear weapon before Israel unleashed its campaign of airstrikes targeting Iran beginning Friday. But Iran's uranium enrichment has reached near weapons-grade levels, and on Thursday the UN's atomic watchdog censured Iran for not complying with obligations meant to prevent it from developing a nuclear weapon.

Prime Minister Benjamin Netanyahu, who has made the destruction of Iran's nuclear programme his top priority, said Israel's strikes so far are "nothing compared to what they will feel under the sway of our forces in the coming days.”

In what could be another escalation if confirmed, semiofficial Iranian news agencies reported an Israeli drone struck and caused a “strong explosion” at an Iranian natural-gas processing plant. It would be the first Israeli attack on Iran's oil and natural gas industry. Israel's military did not immediately comment.

The extent of damage at the South Pars natural gas field was not immediately clear. Such sites have air defence systems around them, which Israel has been targeting.

Iran calls nuclear talks unjustifiable

The sixth round of US-Iran indirect talks on Sunday over Iran's nuclear programme will not take place, mediator Oman said. “We remain committed to talks and hope the Iranians will come to the table soon,” said a senior US official, speaking on condition of anonymity to discuss diplomacy.

Iran's top diplomat said Saturday the nuclear talks were “unjustifiable” after Israel's strikes. Abbas Araghchi's comments came during a call with Kaja Kallas, the European Union's top diplomat.

The Israeli airstrikes were the “result of the direct support by Washington,” Araghchi said in a statement carried by the state-run IRNA news agency. The US has said it isn't part of the strikes.

On Friday, US President Donald Trump urged Iran to reach a deal with the US on its nuclear programme, adding that "Iran must make a deal, before there is nothing left.”

US helps to shoot down Iranian missiles

Iran launched its first waves of missiles at Israel late Friday and early Saturday. The attacks killed at least three people and wounded 174, two of them seriously, Israel said. The military said seven soldiers were lightly wounded when a missile hit central Israel, without specifying where.

US ground-based air defence systems in the region were helping to shoot down Iranian missiles, said a U.S. official who spoke on condition of anonymity to discuss the measures.

Israel's main international airport said it will remain closed until further notice.

First responders were looking for survivors and clearing the remnants of a missile that fell on a neighbourhood outside of Tel Aviv early Sunday morning.

An Associated Press reporter saw streets lined with damaged and destroyed buildings, bombed out cars and shards of glass.

Responders used a drone at points to look for survivors in some of the areas that were too hard to access. Some people were fleeing the area with their belongings in suitcases.

More than a few weeks' to repair nuclear facilities

Israel attacked Iran's main nuclear enrichment facility in Natanz. Satellite photos analyzed by AP show extensive damage there. The images shot Saturday by Planet Labs PBC show multiple buildings damaged or destroyed. The structures hit include buildings identified by experts as supplying power to the facility.

UN nuclear chief Rafael Grossi told the Security Council that the above-ground section of the Natanz facility was destroyed. The main centrifuge facility underground did not appear to have been hit, but the loss of power could have damaged infrastructure there, he said.

Israel said it also struck a nuclear research facility in Isfahan, including “infrastructure for enriched uranium conversion,” and said it destroyed dozens of radar installations and surface-to-air missile launchers in western Iran. Iran confirmed the strike at Isfahan.

The International Atomic Energy Agency said four “critical buildings” at the Isfahan site were damaged, including its uranium conversion facility. “As in Natanz, no increase in off-site radiation expected,” it added.

An Israeli military official, speaking on condition of anonymity in line with official procedures, said that according to the army's initial assessment “it will take much more than a few weeks” for Iran to repair the damage to the Natanz and Isfahan nuclear sites. The official said the army had “concrete intelligence that production in Isfahan was for military purposes.”

Israel denied it had struck the nuclear enrichment facility in Fordo, about 100 kilometers (60 miles) southeast of Tehran.

Among those killed were three of Iran's top military leaders: one who oversaw the entire armed forces, Gen. Mohammad Bagheri; one who led the paramilitary Revolutionary Guard, Gen. Hossein Salami; and the head of the Guard's aerospace division, which oversees its arsenal of ballistic missile programme, Gen. Amir Ali Hajizadeh. On Saturday, Khamenei named a new leader for the Revolutionary Guard's aerospace division: Gen. Majid Mousavi.