As Iran welcomed Ayatollah Mojtaba Khamanei as successor to his father, oil prices surged past $100 a barrel, Saudi Arabia battled drones targeting oil fields and Bahrain's energy company warned that it may be unable to fulfil export contracts.

Finance ministers from the G7 were due to meet on the crisis later in the day and, according to current group chair French President Emmanuel Macron, will discuss releasing strategic oil reserves to dampen the pressure on energy prices and protect the world economy.

As the war entered its 10th day,the United Arab Emirates and Kuwait also reported new attacks, and Asian economies reacted immediately.

The Japanese and South Korean stock markets closed down by more than five percent, Filipino motorists queued to fill their tanks and Vietnam prepared to scrap tariffs on fuel imports.

- 'Brutal aggression' -

European markets also opened sharply down and gas prices on the continent soared 30 percent. Since the start of the war, the benchmark WTI oil contract has risen more than 75 percent and Brent more than 60.

Iranian state media said the Assembly of Experts, Tehran's top clerical body, had named the leader despite "the brutal aggression of the criminal America and the evil Zionist regime", then showed a missile ready for launch bearing the slogan "At your command, Sayyid Mojtaba".

Iran's security chief Ali Larijani told Khamenei that his appointment had "caused the hostile and warmongering enemies to despair."

Iran also warned Europe that it would be held responsible for creating the conditions for the US-Israeli attack, by siding with Washington's efforts to re-impose nuclear sanctions on Tehran.

More explosions were heard in Tehran and central Israel as the foes exchanged strikes. At least one Israeli was killed, a man said be be approximately 40, when shrapnel showered a building site, the Magen David Adom emergency service said.

At least 10 explosions were audible in Tel Aviv, Israel's commercial hub, after the military announced it had detected missiles inbound from Iran.

- New leader close to Guards -

Following strikes on Bahrain's Al Ma'ameer oil facility that ignited a fire, the country's state-owned energy company Bapco joined its counterparts in Qatar and Kuwait in declaring "force majeure" -- a warning that events beyond its control may lead it to miss export targets.

The war has triggered concerns about the economies of the Gulf states, hitting their oil and gas sectors but also aviation and tourism.

As governments around the region seek to protect their image as safe havens, Qatari authorities said they have arrested more than 300 people for sharing images online and what they described as "misleading information".

The announcement followed similar but smaller scale arrests and warnings issued in Bahrain, Kuwait, Saudi Arabia and the UAE.

The war came just weeks after Iranian authorities under Ayatollah Ali Khamenei crushed nationwide protests against the government, killing thousands according to rights groups.

The younger Khamenei, appointed to replace the cleric who led Iran for nearly four decades and who was killed in the first wave of US-Israeli strikes, is considered close to Iran's ideological armed force the Islamic Revolutionary Guard Corps (IRGC).

US President Donald Trump had previously dismissed Mojtaba Khamenei as a "lightweight", and insisted again Sunday on ABC News before the announcement that: "If he doesn't get approval from us he's not going to last long."

After similar threats from Israel, a Chinese foreign ministry spokesman warned that Beijing opposes targeting leaders and insists "Iran's sovereignty, security, and territorial integrity should be respected."

Russia's President Vladimir Putin went further, sending the new supreme leader a direct message of support.

"At a time when Iran is confronting armed aggression, your tenure in this high position will undoubtedly require great courage and dedication," Putin said. "Russia has been and will remain a reliable partner."

- Oil price spikes -

As Iran retaliated against its oil-rich Gulf Arab neighbours, the benchmark price for a barrel of crude soared beyond $100 for the first time since Russia's invasion of Ukraine four years ago.

Trump dismissed the price spike, a politically sensitive issue in the United States, as a "small price to pay" for removing the alleged threat of Iran's nuclear programme.

In a sign that the United States does not expect a quick end to the war, the State Department ordered non-emergency staff to leave Saudi Arabia, days after a drone hit the US embassy.

As questions swirl over the length and goals of the war, Trump told the Times of Israel that any decision on when to end hostilities will be a joint one with Israel's Prime Minister Benjamin Netanyahu.

"I think it's mutual... a little bit. We've been talking. I'll make a decision at the right time, but everything's going to be taken into account," Trump said.

- 'Fierce clashes' -

The multi-front war also intensified in Lebanon. Iran-backed militants Hezbollah said they were engaging Israeli forces who landed in eastern Lebanon on 15 helicopters across the Syrian border, and more strikes hit the southern districts of Beirut.

Large plumes of smoke rose from the area after the Israeli military warned it would destroy branches of Al-Qard al-Hassan, a Hezbollah-linked financial firm.

Lebanon was drawn into the conflict last week when Hezbollah attacked Israel in response to the killing of the elder Khamenei.

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