A paramilitary Hashd Shaabi unit said Tuesday the U.S. forces pounded its posts near the border with Syria and killed dozens of its militants, warning that the attack will not go without punishment.

The U.S. forces carried out “heavy bombardment on Monday morning on the posts of Sayyd al-Shuhadaa Brigades in Akashat area near the border with Syria, leaving large number of martyrs and wounded fighters,” the unit said in a statement emailed to Xinhua.

It said that group “holds the U.S. forces the responsibility for the consequences of the action. We declare that it will not go without punishment.”

The Shiite paramilitary unit also called on the Iraqi government to launch a probe into the incident, and urged the government of Iraq to protect border with Syria “in order to deprive the Americans from using the border line to pass their malicious agendas,” according to the statement.

Local media reports said that over 40 fighters from the paramilitary unit were killed and some 30 others wounded by U.S. artillery bombardment on the units posts in western Iraq.

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The incident came as the Iraqi forces, including the predominantly Shiite Hashd Shaabi units and Sunni tribal fighters, are preparing to liberate the IS-held town of Tal Afar, some 70 km west of Mosul.

On July 10, Iraqi Prime Minister Haider al-Abadi officially declared Mosul’s liberation from IS after nearly nine months of fierce fighting to dislodge the extremist militants from their last major stronghold in Iraq.