No one claimed responsibility for the rocket attacks, but video of the assault was shared on Telegram social media channels used by the militias.
U.S. officials have said the American airstrikes carried out a night earlier were meant to stem militia attacks on U.S. forces, but the Iran-backed groups have sworn revenge, raising the prospect of a further escalation.
The Iraqi government condemned the U.S. airstrike against Iranian-linked militias on Iraqi soil early Monday, underscoring how combustible the situation has become. Iraq described the overnight strike as a “blatant” violation of national sovereignty that breached international conventions.
“Iraq reiterates its refusal to be an arena for settling scores,” Prime Minister Mustafa al-Kadhimi said in a statement, urging both sides to refrain from escalation.
The latest violence comes amid rising U.S. concern over the use of small, explosive-laden drones by Iran-backed groups targeting American and Iraqi personnel in Iraq. U.S. officials describe the emerging drone threat as one of the chief concerns for the small U.S. military mission remaining in the country.
The U.S. airstrikes followed a spate of drone strikes early Saturday in Iraq’s Kurdish region. A congressional aide with knowledge of the Biden administration’s decision-making said the attacks involved Iranian-manufactured drones similar to those that have prompted alarm in Washington as they evade detection systems and strike sensitive targets.
Kadhimi is under pressure from Washington to rein in attacks on U.S.-linked targets. But in practice, Iraq’s network of militia groups, some of them backed by Iran, often hold more power than the prime minister does, experts say, heightening the stakes for any confrontation with them.
As if to underscore the point, thousands of Iraqi paramilitary fighters marched Saturday in the eastern province of Diyala as part of an annual parade, attended this year by Kadhimi, that showcased the range of tanks and rocket launchers in their disposal.
Hours earlier in Iraq’s Irbil province, two of the Iran-linked drones landed roughly a mile from where a new U.S. Consulate is being built, according to the congressional aide and the area’s governor.
In the airstrikes that followed, U.S. forces hit one site used in the launch and recovery of armed unmanned aircraft and another targeted site was a logistics hub, said an official, who spoke on the condition of anonymity due to the sensitivity of the situation.
Kataib Sayyid al-Shuhada, an Iran-backed group largely based in Iraq, said that four of its militiamen were killed. Photographs suggested that the youngest among them was in his early 20s.
A U.S. official with knowledge of the strikes said that the deaths appeared to have happened in Syria and that the strike in Iraq had targeted a storage facility with nobody on-site.
Separately, Syrian state media said, without providing evidence, that U.S. strikes hit residential buildings near the border around 1 a.m. local time, killing a child and wounding three residents.
The militia groups that were targeted said they would seek revenge. “We will not remain silent about the continued presence of the American occupation forces,” groups calling themselves the Iraqi Resistance Coordination Commission said in a statement. “We will make the enemy taste the bitterness of revenge.”
During a visit to Rome on Monday, U.S. Secretary of State Antony Blinken said he hoped the U.S. airstrikes would deter future attacks by Iraqi militias. “I think we’ve demonstrated both with the actions taken last night and actions taken previously that the president is fully prepared to act and act appropriately and deliberately to protect U.S. interests, to protect our people, to protect our personnel,” he said, referring to an earlier set of strikes on the Syrian side of the border.
U.S. officials have counted at least six attacks since April that use drones that appear to have been manufactured by Iran or by its proxies.
“President Biden has been clear that he will act to protect U.S. personnel,” Pentagon spokesman John Kirby said. “Given the ongoing series of attacks by Iran-backed groups targeting U.S. interests in Iraq, the president directed further military action to disrupt and deter such attacks.”
Iraqi officials have lobbied their U.S. counterparts to avoid retaliatory strikes on Iraqi soil, arguing that they would complicate the already delicate politics surrounding the remaining U.S.-led coalition forces in Iraq.
That force has been cut in half to roughly 3,000 troops since the start of last year, after the U.S. assassination of Iranian military commander Qasem Soleimani and senior Iraqi militia leader Abu Mahdi al-Muhandis outside Baghdad Airport prompted Iraq’s parliament to urge the expulsion of all U.S. troops.
Despite significant pressure to produce a timetable for the force’s final departure, Iraqi military officials argue that the force’s intelligence and aerial support are still crucial elements in maintaining pressure on Islamic State remnants in Iraq.
The U.S. strikes came after increasingly brazen and sophisticated attacks by Iranian-backed militias on U.S.-linked forces. Officials in Washington say these are probably linked to Kataib Hezbollah, a group that U.S. forces have bombed on several occasions in Iraq.
Increasingly, militiamen are now turning to small, fixed-wing drones that fly too low to be picked up by defensive systems, military officials and diplomats have said. In April, one of the drones hit a CIA hangar in Irbil province, concerning U.S. officials so much that retaliatory military action was briefly considered. A U.S.-led coalition official said that the drone had been tracked to within 10 miles of its target before it strayed into a civilian flight path, making interception too risky.
Fears have been mounting that continuing militia attacks could trigger an escalation in violence between U.S. forces and Iranian-backed groups that operate in the region.
Loveluck reported from London. Mustafa Salim in Baghdad, Dan Lamothe in Washington and Sarah Dadouch in Beirut contributed to this report.