Iraq’s most prominent Shia cleric Grand Ayatollah Ali al-Sistani has vehemently condemned recent US airstrikes on several bases of the Iraqi Popular Mobilization Units (PMU), where more than two dozen fighters were killed.

“The supreme religious authority condemns the criminal aggression that targeted a number of official Iraqi forces and resulted in the martyrdom and wounds of many,” Ayatollah Sistani’s office said in a statement on Monday.

It added that the “illegal practices carried out by some sides” must not be used as a reason to violate Iraq’s sovereignty.

The statement came just a day after US forces conducted airstrikes on a number of Kata’ib Hezbollah bases in the western province of Anbar.

The aerial aggression killed at least 27 individuals and wounded 51 others, according to the latest toll released on Monday by the PMU, commonly known by its Arabic name Hashd al-Sha’abi. The targeted Kata’ib Hezbollah forces belonged to Brigades 45 and 46 of the PMU.

The Pentagon said in a statement on Sunday evening that the raids targeted weapons storage facilities and command control locations, claiming that the bombings were in response to attacks targeting American forces in Iraq.

“Iraqi authorities alone are entitled to deal with these practices and take the necessary measures to prevent them. They are called upon to do so and to ensure Iraq does not become a field for settling regional and international scores and that others do not interfere in its internal affairs,” Ayatollah Sistani added.

PMU fighters played a major role in the liberation of Daesh-held areas to the south, northeast and north of the Iraqi capital Baghdad, after the terrorists launched an offensive in the country, overrunning vast parts in lightning attacks.

Iraq's caretaker Prime Minister Adel Abdul Mahdi also condemned the US airstrikes.

“The prime minister described the American attack on the Iraqi armed forces as an unacceptable vicious assault that will have dangerous consequences,” his office said in a statement on Monday, adding that Baghdad will announce its official stance following a meeting of the National Security Council later in the day.

Iraqi government threatens to review ties with US

In a related development, Iraq's government threatened on Monday to "review" its relations with the US after deadly airstrikes against the Popular Mobilization Units.

"American forces acted on their political priorities, not those of the Iraqis," AFP quoted the Iraqi government, which is acting in a caretaker capacity following the resignation of Prime Minister Adel Abdel Mahdi, as saying in a statement following a meeting of the country's National Security Council.

It added that the protection of Iraq, its military bases and forces in the country "is the sole responsibility of the Iraqi security forces."

The statement went on to note that such strikes "violate the sovereignty of Iraq" and "contravene the rules of engagement of the (US-led international) coalition."

The attacks "force Iraq to review its relations [with the United States] and its security, political and legal framework to protect its sovereignty."

Separately on Monday, at least 100 Iraqi lawmakers signed a petition calling for discussion of the US airstrikes in parliament, the Arabic-language al-Sumaria television network reported.

Reza al-Haider, the chairman of Iraqi Parliament's Security and Defense Commission, invited the parliament to hold an emergency session to discuss the US aggression on the PMU bases in Qaim, a town located nearly 400 kilometers northwest of the capital near the Syrian border.

He described the aggression as an attack on the Iraqi military and sovereignty, calling on the international community to take an immediate and explicit stance on US interference in the affairs of various countries and its disrespect for their sovereignty.

A view of the petition by Iraqi lawmakers that calls for an emergency meeting in parliament to discuss recent US airstrikes, December 30, 2019

Additionally on Monday, Russia's Foreign Ministry also branded the strikes as “unacceptable and counterproductive,” urging all sides to avoid fuelling tensions in the region.

"We consider such actions unacceptable and counterproductive. We call upon all parties to refrain from further actions that could sharply destabilize the military-political situation in Iraq, Syria, and the neighboring countries," a ministry statement said.

Also on Monday, Syria denounced the US attack on Iraq’s Popular Mobilization Forces, expressing full solidarity with Iraq and its people, the official SANA news agency reported.

An official source at the Foreign and Expatriates Ministry of Syria said the country denounces the US attack on the Popular Mobilization Forces, which defend Iraq’s sovereignty and independence.

The unnamed sources also denounced any act of aggression that targets the sovereignty, independence, and freedom of Iraq and its people.

The source added that Syria expresses its full solidarity with Iraq’s people and institutes, and reiterates its call on the US to not interfere in the internal affairs of Iraq.

The source concluded by offering condolences to the families of those killed and injured in US strikes.

The US invaded Iraq in 2003 under the pretext of “war on terror.” The invasion was followed by rampant violence blamed largely on widespread opposition inside the country to the foreign presence.

In June 2014, Iraq was attacked by Daesh. The issue of Daesh had reared its ugly head amid the volatility.

Washington amassed a coalition soon afterwards, and began renewed wholesale operations in the country.

The terrorists, however, reportedly resurfaced in Iraq recently, despite the presence there of around 5,000 US troops, and large-scale operations carried out by the coalition, which would mostly feature indiscriminate bombings.

Iraqi cleric Moqtada al-Sadr also said on Monday that he is willing to work with the country’s popular forces to end the United States military presence in Iraq through political and legal means.

Reuters quoted him as saying that if this process does not work, he will "take other actions" in cooperation with popular forces to kick out US troops.