Attacks by Iraq's Kataib Hezbollah terrorist against US interests on Friday are the start of "new rules of engagement," a security official from the group said in a social media post.
The Iran-aligned group, while not claiming responsibility for a rare attack on the US embassy in Baghdad on Friday, claimed the embassy was a forward operating base for planning military operations.
The attack was condemned by the US and by Iraqi Prime Minister Mohammed Shia al-Sudani, who said it was an act of terrorism against a diplomatic mission.
But Kataib Hezbollah (KH) said the facility was a base involved in planning military operations. Those who described it as a diplomatic mission were "subservient" and self-interested, Abu Ali al-Askari, a security official from the group, said in a social media post.
US Defense Secretary Lloyd Austin, in a Friday call with Sudani, singled out KH and another group, Haraket Hezbollah al-Nujaba, for the recent targeting of US personnel and said the US reserved its right to respond.
Iran-backed terrorists target Israeli allies
US officials have reported more than 80 attacks against US interest in Iraq and Syria since mid-October, most claimed by an umbrella-group of Iran-aligned Iraqi terrorists over Washington's backing of Israel in its war in Gaza.
The group, which goes by the Islamic Resistance in Iraq, claimed 11 attacks against US forces on Friday, the most in a single day since they began in mid-October.
Sudani has ordered security forces to investigate the embassy attack and on Saturday replaced the regiment in charge of security in Baghdad's highly fortified Green Zone area where the attacks occurred, according to his office.
In an apparent challenge to Sudani, KH said that members of Iraq's security forces that were cooperating with US forces were "accomplices in its crimes."
As well as diplomatic staff in Iraq, the United States has about 2,500 troops in the country on a mission it says aims to advise and assist local forces battling remnants of Islamic State, which in 2014 seized large swathes of both Iraq and Syria before being defeated.