WASHINGTON - The US launched airstrikes against Iranian forces and allied militias in Iraq and Syria on Friday as it began its retaliation for a drone attack that killed three US soldiers in Jordan last week.

Dozens of strikes launched by long-range bombers flown from the US targeted Iran’s Revolutionary Guards Corps (IRGC) Quds Force and affiliated militia groups just hours after president Joe Biden received the remains of the three service members at Dover Air Force Base in Delaware.

Mr Biden said in a statement that he had ordered US military forces to strike at “facilities that the IRGC and affiliated militia use to attack US forces.”

“Our response began today. It will continue at times and places of our choosing. The United States does not seek conflict in the Middle East or anywhere else in the world. But let all those who might seek to do us harm know this: If you harm an American, we will respond,” Mr Biden said.

The strikes began at midnight local time and hit more than 85 targets with more than 125 precision munitions, the Pentagon said in a statement. They targeted four locations in Syria, and three in Iraq.

“The facilities that were struck included command and control operations, centers, intelligence centers, rockets, and missiles, and unmanned aired vehicle storages, and logistics and munition supply chain facilities of militia groups and their IRGC sponsors who facilitated attacks against U.S. and Coalition forces,” the statement said.

It is yet unclear what impact the strikes will have on the militias after many claimed to have evacuated bases or went into hiding after days of US warnings that a “multi-tiered” response was imminent. White House National Security Council spokesman John Kirby said the Pentagon was still assessing the results of the military action, “but we believe that the strikes were successful.”

The decision to strike directly at the IRGC marks a significant escalation in a volatile regional power struggle that pits the US against Iran and a network of allied armed groups across the Middle East. Previous US airstrikes have targeted only the militias, but not their backer.

US forces in the region have come under frequent attack for years by Iran-linked militias opposed to their presence in the region, but those attacks have increased dramatically in the wake of the 7 October attacks on Israel by Hamas militants, and Israel’s invasion of Gaza in response.

US bases have been struck by more than 160 rocket and drone attacks in Iraq and Syria since mid-October by Iran-backed militias who view the US as complicit in the devastation caused by the Gaza war due to its support for Israel. US warships and international merchant vessels have come under frequent attack from Yemen’s Houthi rebels, who are also backed by Iran.

Concerns have been growing over the spread of violence across the Middle East linked to Israel’s war in Gaza, which was triggered by an attack by Hamas inside Israel in which around 1,200 people were killed and another 240 taken hostage. Israel’s war against Hamas, which is allied with Iran, has drawn in Iran’s allies from across the region – from Yemen’s Houthis to Lebanon’s Hezbollah. Israel’s war has killed more than 26,000 Palestinians, mostly women and children, according to the Hamas-run Palestinian health ministry, which the United Nations and other aid groups deem reliable.

The Biden administration has said repeatedly that it hoped to prevent a wider regional escalation as a result of the Israel-Hamas war, but the intervention of the Houthis and the killing of US soldiers has resulted in a series of military confrontations that resemble a low-level regional war. The US now regularly carries out strikes against the Houthis in Yemen, as well as Iran-backed militias in Iraq and Syria.

When questioned by The Independent about whether the US classifies the fighting on multiple fronts as a war, Mr Kirby said he disagreed.

“There were attacks against our troops and facilities in Iraq and Syria well before 7 October – certainly in the last administration as well,” he said on Thursday. “And as for the Houthis, they can claim all they want that this is linked to Gaza but two-thirds of the ships that they’re hitting have no connection to Israel whatsoever. So, it’s just not true. It’s a falsehood.”

Other White House officials contacted by The Independent have shied away from even the suggestion that the series of interconnected conflicts in which the US is embroiled constitutes a regional war, and Mr Biden has insisted that he does not need to seek approval from Congress before this or any other retaliatory strikes against the Iran-backed militias, including strikes against the Houthis carried out by American and British forces over the last several weeks.

These latest strikes, which US officials have privately described as the opening salvos in what will be a longer retaliatory campaign, come after three US service personnel were killed and 34 wounded by a drone strike on a military outpost in Jordan known as Tower 22, on the border between Iraq and Syria. It marked the first time US soldiers have been killed by the attacks since the start of the Israel-Hamas war.

The Pentagon named the fallen soldiers on Monday as Sgt. William Jerome Rivers, 46, of Carrollton, Georgia; Spc. Kennedy Ladon Sanders, 24, of Waycross, Georgia; and Spc. Breonna Alexsondria Moffett, 23, of Savannah, Georgia.

The White House said it had determined that the attack was carried out by a loose alliance of Iran-backed militias in the region.

“We believe that the attack in Jordan was a plan resourced and facilitated by an umbrella group called the Islamic Resistance in Iraq, which contains multiple groups, including Kataib Hezbollah,” Mr Kirby said.

US secretary of defence Lloyd Austin said on Thursday that the military response to those deaths will be “multi-tiered”.

“Again, we have the ability to respond a number of times, depending on what the situation is,” he added.

Following the strikes on Friday, he reiterated that more strikes were likely to follow.

“This is the start of our response. The President has directed additional actions to hold the IRGC and affiliated militias accountable for their attacks on US and Coalition Forces,” he said in a statement.

President Biden told reporters on Wednesday that he had decided on a response to the attacks but did not want an escalation in fighting.

“I don’t think we need a wider war in the Middle East. That’s not what I’m looking for,” he said.

Syrian state media reported on Friday that an “American aggression” had caused casualties and injuries in an area near the Iraq-Syria border.