The Pentagon announced Sunday it had conducted retaliatory targeted air strikes against "facilities used by Iran-backed militia groups" on the Iraq-Syria border, which a monitor said killed at least five militia fighters.

The strikes come at a delicate moment as the United States blames Iran-linked Iraqi factions for recent attacks against Iraqi installations housing its personnel, while also hoping to work out a return to a nuclear deal with Tehran.

"US military forces earlier this evening conducted defensive precision air strikes against facilities used by Iran-backed militia groups in the Iraq-Syria border region," Pentagon spokesman John Kirby said in a statement, adding that the attacks were carried out at the direction of President Joe Biden.

While the United States did not provide information on casualties, the Britain-based Syrian Observatory for Human Rights said that "at least five Iran-backed Iraqi militia fighters were killed and several others were wounded in an attack by US warplanes" on the Syrian side of the frontier.

The war monitor, which relies on a network of sources inside Syria to collect information, said that military positions were among the targets hit.

Syria's state-run SANA news agency said one child had been killed and that at least three other people were wounded.

Kirby said that the targets -- two in Syria, one in Iraq -- were selected because "these facilities are utilized by Iran-backed militias that are engaged in unmanned aerial vehicle (UAV) attacks against US personnel and facilities in Iraq."

Kataeb Hezbollah and Kataeb Sayyid al-Shuhada, two hardline Iraqi military factions with close ties to Tehran, were among the "several Iran-backed militia groups" that had used the targeted facilities, Kirby said.

Since the start of the year there have been more than 40 attacks against US interests in Iraq, where 2,500 American troops are deployed as part of an international coalition to fight the jihadist Islamic State group.

The vast majority have been bombs against logistics convoys, while 14 were rocket attacks, some of them claimed by pro-Iran factions that aim to pressure Washington into withdrawing all their troops.

"Given the ongoing series of attacks by Iran-backed groups targeting US interests in Iraq, the president directed further military action to disrupt and deter such attacks," Kirby said.

"Specifically, the US strikes targeted operational and weapons storage facilities at two locations in Syria and one location in Iraq, both of which lie close to the border between those countries," he added.

The Pentagon said that it had conducted airstrikes targeting "two locations in Syria and one location in Iraq"
The Pentagon said that it had conducted airstrikes targeting "two locations in Syria and one location in Iraq" AFP / STAFF

The move marks the second such US attack on Iran-backed militia in Syria since Biden took office, with the first having occurred in February with a strike on facilities in the country's east that left more than 20 fighters dead, according to the Observatory.

On a separate, diplomatic front, the US-issued strikes come two days after the United States and France warned Iran that time was running out to return to a nuclear deal, expressing fear that Tehran's sensitive atomic activities could advance if talks drag on.

A return to the 2015 Iran accord has been a key Biden promise after the nuclear deal was trashed by his predecessor Donald Trump.

"We have a national interest in trying to put the nuclear problem back in the box that it was in the JCPOA," US Secretary of State Antony Blinken said, using the acronym for the accord's formal name.

The UN nuclear watchdog said Friday it had received no reply from Tehran over the possible extension of a temporary agreement covering inspections at Iranian nuclear facilities which expired on Thursday.

Meanwhile, Iraqi Kurdish officials said Saturday three explosives-laden drones hit near the northern Iraqi city of Arbil, where the United States has a consulate.

The attack also occurred as the Hashed al-Shaabi, a pro-Iran paramilitary alliance opposed to the US presence in Iraq, held a military parade near Baghdad attended by senior officials.

In April, a drone packed with explosives hit the coalition's Iraq headquarters in the military part of the airport in Arbil, the Iraqi Kurdish regional capital.

The tactic poses a headache for the coalition, as drones can evade air defenses.

"As demonstrated by this evening's strikes, President Biden has been clear that he will act to protect US personnel," Kirby said Sunday.

Announcement of the strikes came one day before Biden meets at the White House with Reuven Rivlin, president of Israel, Iran's arch foe.