Iraq's prime minister in a statement Saturday declared a three-day national mourning over the killings of top Iranian commander Qasem Soleimani, senior commander of Iraq’s Hashd al-Shaabi force Abu-Mahdi al-Muhandis, and 8 others in a U.S. drone airstrike early Friday in the capital Baghdad. 

According to the statement, Adil Abdul-Mahdi declared "three days of mourning for the martyrs."

In the attack, along with Soleimani and al-Muhandis, Iranian officers and five Iraqis were also killed.

Iranian Supreme Leader Ali Khamenei, who gave Soleimani the country’s highest honor last year, vowed "severe retaliation" in response to his killing.

Soleimani was the long-time commander of Iran's Revolutionary Guards' Quds Force, which was designated a terror group by the U.S. The group is estimated to have 20,000 members.