WASHINGTON, DUBAI, CAIRO: The United States and Israel attacked Iran on Saturday, targeting its top leaders and calling for the overthrow of its government, while Iran responded with missiles fired at Israel and neighbouring Gulf countries.

President Donald Trump said the strikes were aimed at ending a security threat to the United States and ensuring Iran could not develop a nuclear weapon. He called on Iranian security forces to lay down their weapons and invited Iranians to topple their government once the bombing ended.

Tehran called the strikes, which began in the morning hours and hit targets across the country, unprovoked and illegal. Iran's Al-Alam television said Supreme Leader Ayatollah Ali Khamenei - yet to be heard from by Saturday evening - was due to give a speech soon.

Iran responded to the strikes by launching missiles at Israel and at several Gulf Arab allies of the United States that host American bases.

It promised a stronger response to come, with a senior Iranian Revolutionary Guards commander, Ebrahim Jabbari, saying it had so far used only "scrap missiles" and would soon unveil unforeseen weapons, state television reported.

Israel said it hit strategic defence systems, including a SA-65 aerial defense system located in the Kermanshah area in western Iran, further weakening air defences it had already damaged in strikes last year.

Iran's Defence Minister Amir Nasirzadeh and Revolutionary Guards commander Mohammed Pakpour were killed in Israeli attacks, three sources familiar with the matter said.

Explosions rang out in nearby oil-producing Gulf Arab countries, which said they had intercepted missiles after Tehran warned it would strike the region if it was attacked.

The first wave of strikes in what the Pentagon named "OPERATION EPIC FURY" mainly targeted Iranian officials, a source familiar with the matter said.

An Israeli official said Khamenei and Iranian President Masoud Pezeshkian were both targeted but the result of the strikes was not clear. A source with knowledge of the matter had earlier told Reuters that Khamenei was not in Tehran and had been transferred to a secure location.

An Iranian source close to the establishment said several senior commanders in Iran's Revolutionary Guards and political officials had been killed. Iranian state media said 40 people were killed in an Israeli airstrike on a school. Reuters could not independently confirm the reports.

TRUMP SAYS 'BOMBS WILL BE DROPPING EVERYWHERE'

In a video message published on social media, Trump cited Washington's decades-old dispute with Iran and Iranian attacks, dating to the seizure of the U.S. embassy in Tehran during the 1979 Islamic revolution that brought the clerics to power.

Trump, who had deployed vast U.S. military firepower in the region saying he hoped to force Iranian concessions in nuclear talks, said the operation was intended to ensure Tehran did not obtain a nuclear weapon. The aim was "eliminating imminent threats from the Iranian regime".

He urged Iranians to stay sheltered because "bombs will be dropping everywhere". But he added: "When we are finished, take over your government. It will be yours to take. This will be probably your only chance for generations."

Israeli Prime Minister Benjamin Netanyahu said the joint U.S.-Israeli attack "will create the conditions for the brave Iranian people to take their destiny into their own hands" and "remove the yoke of tyranny".

Iran's clerical leaders were already in a difficult position after mass anti-government demonstrations in January, which led to a crackdown in which thousands of people were killed, the worst domestic unrest since the era of the 1979 revolution.

Protesters had again taken to the streets in recent days in remembrance of those killed the previous month.

Israeli military operations over the past two years have already killed some of Iran's senior military officials and severely weakened several of Tehran's once-feared proxy forces across the Middle East.

After Israel pounded Iran in a 12-day air war last June joined by the United States, the U.S. and Israel had warned that they would strike again if Iran pressed ahead with its nuclear and ballistic missile programmes. The threats were backed up in recent weeks by a U.S. military buildup in the region, even as Iranian and U.S. officials held nuclear talks.

An Israeli defence official said the operation had been planned for months in coordination with Washington, and that the launch date was decided weeks ago.

MISSILES FIRED AT ARAB GULF STATES

Oil markets have been closely watching the standoff between Washington and Tehran to try and determine if supplies will be impacted.

"If we don’t see signs of de-escalation over the weekend, risk premiums could still drive Brent up" by $10–$20 per barrel when markets reopen on Monday, said Jorge Leon, head of geopolitical analysis at Rystad Energy.

Iran, the third largest producer in the Organization of the Petroleum Exporting Countries, pumps about 4% of global oil supplies, and a far larger share is shipped past its coast through the strait leading out of the Gulf.

Iran's Revolutionary Guards said all U.S. bases and interests in the region were within Iran's reach and that Iran's retaliation would continue until "the enemy is decisively defeated". Iraq's Iran-aligned armed group Kataib Hezbollah said it would soon attack U.S. bases in the region.

Saudi Arabia's Crown Prince Mohammed bin Salman called United Arab Emirates President Sheikh Mohammed bin Zayed Al Nahyan to discuss the Iranian attacks, the UAE state news agency said.

Loud booms sounded in Abu Dhabi, capital of the United Arab Emirates, an oil producer and close U.S. ally, and several blasts were heard in the business capital Dubai.

Bahrain said the service centre of the U.S. Fifth Fleet - base for American naval forces in the region - had been subjected to a missile attack. Video footage showed a thick grey plume of smoke rising from near the island state's coastline as sirens wailed.

Qatar said it had downed all missiles targeting the country and that it had a right to respond. Kuwait confirmed a missile attack on a U.S. military base there.

An explosion was heard in Iran's southeastern port city of Chabahar, Iranian state media reported.

Israel's military did not immediately respond to a request for comment on the report of a strike at a primary school for girls in southern Iran, where Iranian state media reported 40 deaths.

In Israel, police said all holy sites were closed to visitors under national emergency guidelines after authorities announced several barrages of missiles were launched from Iran.

Global airlines cancelled flights across the Middle East and the attacks raised the prospect of oil prices rising. Some oil majors and trading houses suspended crude oil and fuel shipments via the Strait of Hormuz, four trading sources said.