Most of the hundreds of drones and missiles launched by Iran in a retaliatory strike were downed before reaching Israeli territory, though a young girl was critically injured and the region remains braced for further escalation.

Iran's Foreign Minister Hossein Amirabdollahian said on Sunday Iran had given neighbouring countries and Israel's ally the United States 72 hours' notice it would launch the strikes, a move that would have enabled them to largely thwart the attack.

Turkey's Foreign Ministry said it had spoken to both Washington and Tehran before the attack, adding it had conveyed messages as an intermediary to be sure reactions were proportionate.

"Iran said the reaction would be a response to Israel’s attack on its embassy in Damascus and that it would not go beyond this. We were aware of the possibilities. The developments were not a surprise," said a Turkish diplomatic source.

However, a senior official in the administration of U.S. President Joe Biden denied Amirabdollahian's statement, saying Washington had had contact with Iran through Swiss intermediaries but did not get 72 hours' notice.

"That is absolutely not true,” the official said. “They did not give a notification, nor did they give any sense of ... 'these will be the targets, so evacuate them.'"

Tehran sent the United States a message only after the strikes began, and the intent was to be "highly destructive" said the official, speculating that Iran was saying it had given notice in order to cover embarrassment at the attack's failure.

"We received a message from the Iranians as this was ongoing, through the Swiss. This was basically suggesting that they were finished after this, but it was still an ongoing attack. So that was (their) message to us," the U.S. official said.

However, Iraqi, Turkish and Jordanian officials each said Iran had provided early warning of the attack last week, including some details.

The attack with drones, cruise missiles and ballistic missiles risked causing terrible casualties and triggering massive Israeli and U.S. retaliation that could have spiralled into a regional conflagration.

U.S. officials said on Friday and Saturday they expected an imminent attack and urged Iran against one, with Biden tersely saying his only message to Tehran was: "Don't."

ESCALATION

Two Iraqi sources, including a government security adviser and a security official, said Iran had used diplomatic channels to inform Baghdad about the attack at least three days before it happened.

The exact timing of the attack was not disclosed at that point, but was passed to Iraqi security and military authorities hours before the strikes, allowing Baghdad to close its airspace and avoid fatal accidents.

"The government clearly understood from the Iranian officials that the U.S. military in Iraq was also aware of the attack in advance," said the Iraqi security official.

A senior Jordanian official said Iran had summoned Arab envoys in Tehran on Wednesday to inform them of their intention to carry out an attack, though it did not specify the timing.

Asked if Iran had also given details about the targets and kind of weapons to be used, the Jordanian source did not respond directly but gave an indication that that was the case.

An Iranian source briefed on the matter said Iran had informed the U.S. through diplomatic channels that included Qatar, Turkey and Switzerland about the scheduled day of the attack, assuring it would be conducted in a manner to avoid provoking a response.

How far escalation can be avoided remains in question. Biden has told Israel the United States will not join any Israeli retaliation, the U.S. official said.

However, Israel is still weighing its response and will "exact the price from Iran in the fashion and timing that is right for us", Israeli minister Benny Gantz said on Sunday.