US defence systems shot down an armed drone over Ain Al Asad airbase that hosts American, Iraqi and other international forces in western Iraq, government sources said.
The attack on Monday, which the sources said did not cause casualties or damage, came hours after a drone was shot down on Sunday over Erbil Airport in northern Iraq where US and other international forces are stationed.
It is one of scores of drones and rockets launched by Iran-backed militias in a sharp escalation of attacks following Israel’s war in Gaza, which has killed more than 21,800 people.
The groups, which analysts say are front organisations for Iran-backed and Iraqi government-funded militias Asaib Ahl Al Haq, Harakat Al Nujaba and Kataib Hezbollah, operate under an umbrella organisation called the Islamic Resistance in Iraq.
Such groups are among around 50 government-funded militias in the Popular Mobilisation Forces.
Iraq seeks to 'end presence' of US-led forces in country
Tensions between the militias and the US have risen again after US retaliatory air strikes against the groups, part of a conflict that has simmered and occasionally flared up since US forces withdrew the bulk of troops in 2011.
About 2,500 have been in Iraq, a holdover force from the 2014-2018 war against ISIS, who remain to train and advise the official Iraqi army.
Authorities in Iraqi Kurdistan meanwhile said on Sunday that two drones struck a military base used by the autonomous region's security forces, blaming the attack on “outlaws” funded by Baghdad.
The attack on the base in Erbil province was carried out on Saturday and caused some damage but no casualties, the regional government said.
The region's Peshmerga forces are allies of the US-led anti-ISIS coalition that has several thousand international troops deployed in Iraq.
There was no immediate claim for the attack.
A tally by US military officials has counted 106 attacks against its troops in Iraq and Syria since October 17.
Masrour Barzani, Prime Minister of Iraqi Kurdistan said he was “deeply alarmed” by Saturday's drone attack.
“I condemn the outlaws and their collaborators in the strongest terms possible,” he said on X, formerly Twitter.
The regional government said these groups “are funded by the federal government” in Baghdad, with which it has strained relations.
The government of Prime Minister Mohammed Shia Al Sudani is backed by pro-Tehran parties.
Mr Al Sudani's office said on Sunday he “had ordered a thorough investigation into this criminal (drone) attack”, in co-ordination with the Iraqi Kurdish security services.
