Iran-backed armed groups in Iraq are considering the fate of a truce with US-led coalition forces following the killing of at least four of its members in a US strike on a Popular Mobilisation Forces' base in Babil province, south of Baghdad, on Tuesday night.
The PMF, an umbrella term for groups of armed fighters that are officially part of the Iraqi security forces, confirmed members of its 47th Brigade had been killed in an attack carried out "by missiles fired from drones".
The brigade belongs to Kataib Hezbollah, one of the most fiercely anti-US groups within the PMF.
“The Iraqi factions will respond to the Israeli and American crimes, and will support the 'Axis of Resistance' in every step they take,” Haider Al Lami, a member of the political council of Al Nujaba Movement in Iraq, told The National.
"All Israeli sites will become targets and within reach of the fire of Iraqi factions."
The number of PMF fighters killed was mentioned on a Telegram channel affiliated with the group, although the PMF's central media unit did not confirm the death toll.
In a statement, Kataib Hezbollah, another Iran-backed faction, said it would decide on "an appropriate response" after discussions with groups in the Islamic Resistance in Iraq.
Every decision taken by that group applies to Al Nujaba, Mr Al Lami added, including the issue of the truce that was agreed with US forces present in Iraq and Syria.
"The Zionists and the Americans have opened the doors of hell on themselves," Akram Al Kaabi, Al Nujaba's leader, said in a statement on X. "They will not succeed in their cowardly acts."
Al Nujaba Movement is a member of the Islamic Resistance in Iraq, a coalition of Iran-backed groups that has claimed scores of attacks on US forces stationed in Iraq and Syria since the Israeli war on Gaza started on October 7.
The warring parties agreed to an unofficial truce early this year, which has generally held despite sporadic attacks on US troops. The lull was aimed at preventing escalation after the killing of three US soldiers at the Iraq-Jordan border and to allow scope for negotiations around the departure of US troops from Iraq.
But the calm may end after the strikes on Tuesday night, Iraqi armed groups warned.
A senior Iraqi army official was more cautious about the possibility of the truce ending and expected the PMF would not want an escalation.
"There is a possibility [of the truce ending] but the chances are low, because in the end, the PMF submits to the status quo – they will be quiet and not retaliate," the official said on condition of anonymity. "They are really scared of the United States because it targets them in precise operations using drones."
Iraq condemned the strike on the PMF base, calling it "a heinous crime and blatant aggression".
Maj Gen Yahya Rasool, an Iraqi military spokesman, said the attack was a "serious violation" of the US forces' mission and mandate in Iraq, where they are assisting the country's military in counter-ISIS operations.
"Such serious and uncalculated transgressions can significantly undermine all efforts, mechanisms and frameworks of joint security work to combat ISIS in Iraq and Syria," he said in a statement. "They also risk dragging Iraq and the entire region into dangerous conflicts and wars."
The attack took place at Jurf Al Sakhr, an area Babil widely known as a PMF base used by Kataib Hezbollah.
The strikes came as violence between Israel and Iran-backed Hezbollah and Hamas escalated dramatically across the region.
The latest escalation comes as the fate of a senior Hezbollah commander Fuad Shukr remains unknown after an Israeli strike on Beirut's southern suburbs on Tuesday night. A suspected Israeli attack on Tehran killed Hamas politburo leader Ismail Haniyeh.
The US said it carried out what it described as a "self-defence air strike" on fighters who were trying to launch drones that were deemed a threat to US and allied troops.
About 2,500 US troops are stationed in Iraq as part of the international coalition against ISIS.
Kataib Hezbollah claimed the attack targeted "drone experts" who were preparing surveillance drones that would be used to secure Karbala during the imminent Arbaeen pilgrimage. The event involves millions of mostly Shiite Muslims visiting the holy city and has previously been the target of suicide bombings.
There has been a significant push by Baghdad and the Iran-backed factions for the coalition to leave Iraq. The Iraqi and US governments held talks last week in Washington, where they put the final touches on a withdrawal deal and a post-departure security relationship.