The United States and Britain struck at least 36 Houthi targets in Yemen in a second wave of assaults meant to further disable Iran-backed groups that have relentlessly attacked American and international interests in the wake of the Israel-Hamas war, US officials told The Associated Press.

The latest strikes against the Houthis were launched by ships and fighter jets. The strikes follow an air assault in Iraq and Syria on Friday that targeted other Iranian-backed militias and the Iranian Revolutionary Guard in retaliation for the drone strike that killed three US troops in Jordan last weekend.

The Houthi targets were in 10 different locations and were struck by US F/A-18 fighter jets from the USS Dwight D. Eisenhower aircraft carrier and by American warships firing Tomahawk missiles from the Red Sea, the US officials said.

According to officials, the USS Gravely and the USS Carney, both Navy destroyers, launched missiles.

They were not authorized to publicly discuss the military operation and spoke on condition of anonymity.

Saturday’s strikes marked the third time the US and Britain had conducted a large, joint operation to strike Houthi weapon launchers, radar sites and drones. But the Houthis have made it clear that they have no intention of scaling back their assault.

The US destroyer Laboon and F/A-18s from the Eisenhower shot down seven drones fired from Houthi-controlled areas of Yemen into the Red Sea, the destroyer Carney shot down a drone fired in the Gulf of Aden and US forces took out four more drones that were prepared to launch.

Hours before the latest joint operation, the US took another self-defence strike on a site in Yemen, destroying six anti-ship cruise missiles, as it has repeatedly when it has detected a missile or drone ready to launch.

An Iraqi militia official hinted at a desire to de-escalate tensions in the Middle East following retaliatory strikes launched by the United States against dozens of sites in Iraq and Syria used by Iranian-backed militias and the Iranian Revolutionary Guard.

Hussein al-Mosawi, spokesperson for Harakat al-Nujaba, one of the main Iranian-backed militias in Iraq, in an interview with The Associated Press in Baghdad condemned the US strikes, saying Washington “must understand that every action elicits a reaction.” But he then struck a more conciliatory tone, saying that “we do not wish to escalate or widen regional tensions.”

Mosawi said the targeted sites in Iraq were mainly “devoid of fighters and military personnel at the time of the attack.”

Syrian state media reported that there were casualties from the strikes but did not give a number. Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said that 23 people, all rank-and-file fighters, were killed.

Iraqi government spokesperson Bassim al-Awadi said in a statement that the strikes in Iraq near the Syrian border killed 16, including civilians, and there was “significant damage” to homes and private properties.

A US official said Saturday that an initial battle damage assessment showed the US had struck each of its planned targets in addition to a few “dynamic targets” that popped up as the mission unfolded, including a surface-to-air missile site and drone launch sites. The official, who spoke on the condition of anonymity to provide details that were not yet public, did not yet have a casualty assessment.

Iraq’s foreign ministry announced Saturday it would summon the US embassy’s chargé d’affaires — the ambassador being outside of the country — to deliver a formal protest over US strikes on “Iraqi military and civilian sites.”

The air assault was the opening salvo of US retaliation for a drone strike that killed three US troops in Jordan last weekend. The US has blamed that on the Islamic Resistance in Iraq, a coalition of Iranian-backed militias.

Iran, meanwhile, has attempted to distance itself from the attack, saying that the militias act independently of its direction.

Iraqi spokesperson al-Awadi condemned the strikes as a violation of Iraqi sovereignty, particularly since some of them targeted facilities of the Population Mobilization Forces. The PMF, a coalition of Iranian-backed militias, was officially brought under the umbrella of the Iraqi armed forces after it joined the fight against the Islamic State in 2014, but in practice it continues to operate largely outside of state control.

The Popular Mobilization Forces said in a statement Saturday that one of the sites targeted was an official security headquarters of the group. In addition to the 16 killed, it said 36 people had been wounded, “while the search is still ongoing for the bodies of a number of the missing.”

The Iraqi government has been in a delicate position since a group of Iranian-backed Iraqi militias calling itself Islamic Resistance in Iraq — many of whose members are also part of the PMF — began launching attacks on US bases in Iraq and Syria on October 18. The group described the strikes as retaliation for Washington’s support for Israel in the war in Gaza.

Behind the scenes, Iraqi officials have attempted to rein in the militias, while also condemning US retaliatory strikes as a violation of Iraqi sovereignty and calling for an exit of the 2500 US troops who are in the country as part of an international coalition to fight IS. Last month, Iraqi and US military officials launched formal talks to wind down the coalition’s presence, a process that will likely take years.

One of the main Iran-backed militias, Kataib Hezbollah, said it was suspending attacks on American troops following Sunday’s strike that killed the US troops in Jordan, to avoid “embarrassing” the Iraqi government.

Meanwhile Saturday, the US military’s Central Command acknowledged it had had a series of skirmishes in the Red Sea and the Gulf of Aden with Yemen’s Houthi rebels. On Friday, the USS Carney shot down a drone over the Gulf of Aden and there were no injuries or damage. The US also conducted airstrikes on four Houthi drones preparing to launch that it said “presented an imminent threat to merchant vessels and the US Navy ships in the region.”

Overnight, F/A-18 fighter jets from the USS Dwight D. Eisenhower aircraft carrier, along with the USS Laboon, shot down seven drones in the Red Sea.