Tehran, Iran - Israel traded fire with Hezbollah in Lebanon on Monday and continued attacks on Iran as the regional war unleashed by US-Israeli attacks entered its third day.

The Lebanese Health Ministry reported that at least 31 people were killed and 149 others injured in preliminary figures from the southern suburbs of Beirut and southern regions of the country.

Hezbollah had fired rockets at Israel in retaliation to the killing of Iran's supreme leader, Ayatollah Ali Khamenei, whose death was confirmed Sunday morning.

US President Donald Trump also vowed to avenge the deaths of three American service members and said the war with Iran could last for weeks.

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Iran's Revolutionary Guards said Monday they had launched missile strikes on Israeli targets, including Prime Minister Benjamin Netanyahu's office and other sites in Tel Aviv, Haifa, and east Jerusalem, calling it a "tenth wave" of attacks. A British base in Cyprus was also reportedly hit.

Here are the latest developments in the sprawling conflict.

A total of six US military personnel have been killed since the start of the Iran war, US Central Command (CENTCOM) said Monday, raising the death toll from four.

"US forces recently recovered the remains of two previously unaccounted for service members from a facility that was struck during Iran's initial attacks in the region," CENTCOM said in a post on X.

Iran accused Israel and the US on Monday of having attacked its nuclear facility at Natanz, one of the main targets of the previous conflict between the three countries last June.

"The criminal regimes of the United States and Israel, pursuing their aggression, again targeted the Natanz nuclear site on Sunday afternoon in two brutal attacks," Iran's atomic energy chief Mohammad Eslami said in a letter to the UN's nuclear watchdog, as quoted by the IRNA news agency.

The UN agency's head had said on Monday that there was "no indication" any nuclear installations had been hit.

Iranian President Masoud Pezeshkian on Monday said his country "will not remain silent" after what he described as US-Israeli strikes on a school and a Tehran hospital.

"Attacks on hospitals strike at life itself. Attacks on schools target a nation's future... The world must condemn it," he wrote on X.

"Iran will not remain silent or yield to these crimes," he added.

Iran has claimed 168 were killed at the school in the south on Saturday, but neither the US nor Israel has confirmed the strike, while the incident at Tehran's Gandhi hospital took place on Sunday.

Iran, which launched retaliatory action in the Middle East after US-Israeli strikes since the weekend, bears no ill will towards Gulf countries, its foreign minister said on Monday.

"Iran harbors no hostility towards the Persian Gulf countries and is determined to pursue good neighbourly relations with them," Abbas Araghchi said during a phone call with his Chinese counterpart, Wang Yi.

According to his ministry, Araghchi said Iran's "defensive response against US military bases... should not be seen as an Iranian attack against these countries."

Saudi Arabia's military raised its readiness levels after multiple attacks by Iran, a source close to the army told AFP on Monday, while another warned of a possible military response if its oil infrastructure is targeted.

The massive Ras Tanura refinery on Saudi Arabia's Gulf coast went into partial shutdown on Monday after a strike by drones, three days into the Middle East war.

The complex run by the Saudi state oil giant Aramco is home to one of the largest refineries in the entire Middle East and a cornerstone of the kingdom's energy sector. The complex has a capacity of 550,000 barrels per day.

"The Saudi army has raised its readiness to full alert," the source close to the military told AFP after the incident.

The US military announced that a fourth American service member had been killed in the war on Iran.

"As of 7:30 AM ET, March 2, four U.S. service members have been killed in action. The fourth service member, who was seriously wounded during Iran's initial attacks, eventually succumbed to their injuries," US Central Command (CENTCOM) wrote on X.

"The identities of the fallen are being withheld until 24 hours after next of kin notification," it added.

The Israeli military said on Monday it had begun a new "broad strike" in the "heart of Tehran" after generals vowed to step up attacks on "key elements of the regime".

Loud explosions were heard on Monday in several parts of the Iranian capital, AFP journalists said, shaking apartment buildings in the center.

Iran also hit targets across the Gulf, with the army saying it had launched 15 cruise missiles in strikes on a US air base in Kuwait – where black smoke was seen rising over the US embassy – and vessels in the Indian Ocean.

A power plant in Qatar was hit, one person was killed as an oil tanker was targeted off Oman, and British officials said a vessel in a Bahrain port had been struck by "unknown projectiles".

Three F-15E Strike Eagles were mistakenly shot down by Kuwait air defences late on Sunday night, the US Central Command said.

"During active combat – that included attacks from Iranian aircraft, ballistic missiles, and drones – the US Air Force fighter jets were mistakenly shot down by Kuwaiti air defenses," CENTCOM said Monday, adding that all six aircrew ejected and were safe.

"Kuwait has acknowledged this incident, and we are grateful for the efforts of the Kuwaiti defense forces and their support in this ongoing operation," it added.