Tehran, Iran - Israel launched airstrikes on Iran early on Saturday, with US forces reportedly participating in the unprovoked attack.

"The State of Israel has launched a preemptive strike against Iran. Defence Minister Israel Katz has declared a special and immediate state of emergency throughout the country," read a statement from his ministry.

A US official told Al Jazeera that Washington was participating in the attack, and President Donald Trump confirmed the start of full-blown war in an eight-minute speech.

Two loud blasts were heard in Tehran on Saturday morning by AFP journalists, and two plumes of thick smoke were seen over the center and east of the Iranian capital. Explosion were also reported in other regions of the country, with the Israeli army announcing that government buildings and military installations were being targeted.

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Both Israel and Iran announced the closure of their respective airspaces, as did other states in the region.

Iran responded by launching extensive retaliatory missile attacks. Qatar, which hosts the largest US military base in the Middle East, said it had intercepted a rocket. Bahrain, the United Arab Emirates, Kuwait, and Iraq – all countries with a significant US military footprint – have also reportedly come under fire.

The major escalation came after weeks of threats of war made by President Donald Trump, even as Iran had been participating in intense talks related to its nuclear program. As recently as Friday, officials from Tehran had made guardedly optimistic noises about progress towards a negotiated settlement.

Saturday's opening salvo mirrored the events of June last year, when Israel launched unilateral and unprovoked attacks on Iran while it was engaged in negotiations with Washington.

Israeli strikes hit a girls' school in the southern Iranian province of Hormozgan near the strategic sea route of the Strait of Hormuz, killing and wounding scores, Iranian state media said.

The latest official death toll stood at 40.

Israel's military also said it targeted multiple sites where senior Iranian officials had gathered in the capital Tehran on Saturday morning and was "assessing" the impact of the attacks.

A civilian was killed in Iranian strikes that hit Abu Dhabi on Saturday, the UAE's ministry of defence said in a statement, as Tehran launched attacks across the Gulf in retaliation for US and Israeli strikes.

The defence ministry reported "the fall of some missile debris in a residential area" of Abu Dhabi that "resulted in one civilian death of an Asian nationality".

Iraq's powerful pro-Iran group Kataeb Hezbollah warned Saturday it will start imminent attacks on US bases after air strikes hit an Iraqi military base housing the group.

"We will soon begin attacking American bases in response to their aggression," the group said in a statement.

Two fighters were killed Saturday in air strikes that hit the Jurf al-Sakher base, also known as Jurf al-Nasr, in southern Iraq.