The timing of Israel's plan to attack Iran was top secret. But Washington pizza delivery trackers guessed something was up before the first bombs fell.

About an hour before Iranian state TV first reported loud explosions in Tehran, pizza orders around the Pentagon went through the roof, according to a viral X account claiming to offer "hot intel" on "late-night activity spikes" at the US military headquarters.

Israel's unprecedented strikes on its archfoe Iran Friday are a resounding blow for Tehran that has thrown into doubt its ability to respond militarily, analysts said.

Israel said it hit 100 targets including Iranian nuclear and military sites in the attack.

The airstrikes killed senior figures, among them leaders of the Revolutionary Guards, the armed forces' chief and top nuclear scientists.

Supreme leader Ayatollah Ali Khamenei warned Israel of a "bitter and painful" fate over the attacks.

Gulf countries on Friday unanimously condemned Israel's strikes on Iran, fearing an escalation that could threaten economic interests and security.

"Gulf states are very much caught between a rock and a hard place," Sanam Vakil, director of the Chatham House think-tank's Middle East and North Africa Programme told AFP.

While "they are quietly applauding the further weakening of Iran they face real risks and have to play their cards carefully", she said.

Global airlines on Friday cancelled flights to Tel Aviv, Tehran and other Middle East destinations, or rerouted planes, as airspaces shut following Israeli strikes on Iran.

Israel, Iran, Iraq, Jordan and Syria closed their airspaces after Israel hit military and nuclear facilities in Iran. Israel said Tehran launched drones in retaliation.

Air India's New Delhi-Vienna and Mumbai-London flights were about to enter Iranian airspace when Israel launched its attack, forcing the planes to turn back to their origin, according to aircraft tracker Flight Aware.

Iranians called for revenge on Friday demanding a swift response to a dizzying wave of strikes by Israel, as some took to the streets in protest, while others sheltered inside, unsure what would happen next.

The aerial onslaught killed several of the military's top brass, targeted an array of leading scientists and struck military and nuclear sites across Iran in an unprecedented attack that left many seething with anger.

World leaders urged restraint on Friday after Israel pounded Iran, striking 100 targets including nuclear and military sites, and killing senior figures.

Here is a roundup of key reactions:

- 'Cannot have nuclear bomb': United States -

France's President Emmanuel Macron on Friday urged the US and Iran to resume nuclear talks following a wave of Israeli strikes against Iran.

"Iran bears a heavy responsibility in the destabilisation of the whole region," he said after Western nations in recent days accused Tehran of deliberately escalating its nuclear programme, despite several rounds of US-Iran talks.

"We call for the resumption of dialogue and the reaching of a deal."

Islamic Revolutionary Guard Corps chief Hossein Salami, killed in an Israeli air strike on Tehran Friday, was a veteran officer close to Iran's supreme leader, Ayatollah Ali Khamenei, and known for his tirades against Israel and its main ally, the United States.

"If you make the slightest mistake, we will open the gates of hell for you," the white-bearded general warned Tehran's archenemies during a tour of an underground missile base in January.

Airlines in the Gulf cancelled flights to many Middle East destinations on Friday as some governments closed their airspace following Israeli strikes on Iran.

Emirates, the Middle East's largest airline, said it had cancelled flights to and from Iraq, Jordan, Lebanon and Iran after Israel launched the strikes.

Several flights scheduled for Friday and one Tehran flight on Saturday were listed as cancelled on the airline's website.

Before Israeli strikes on Friday, Washington and Tehran had held several rounds of talks on Iran's nuclear programme, as concerns mounted about its rapid expansion.

Iran has significantly ramped up its nuclear programme in recent years, after a landmark deal with world powers curbing its nuclear activities in exchange for sanction relief began to unravel in 2018 when the United States unilaterally withdrew.