Iran's Supreme Leader Ayatollah Ali Khamenei on Friday warned that a "harsh retaliation is waiting" for the U.S. after an airstrike on an airport in Baghdad killed Iranian Gen. Qassem Soleimani, the head of Iran's elite Quds Force.

The Iranian state TV carried a statement by Khamenei who also called Soleimani "the international face of resistance." Khamenei declared three days of public mourning for the general's death.

Another Iranian foreign minister warned that the U.S. would bear all the consequences of the “foolish” military attack, claiming his assassination would only escalate tensions in the region given that he was “THE most effective force” fighting terrorism carried out by the Islamic State.

Javad Zarif, the foreign minister of Islamic Republic of Iran, said on Twitter that “The US' act of international terrorism, targeting & assassinating General Soleimani—THE most effective force fighting Daesh (ISIS), Al Nusrah, Al Qaeda et al—is extremely dangerous & a foolish escalation.”

“The US bears responsibility for all consequences of its rogue adventurism,” he said.

Zarif references three affiliated Sunni Muslim extremist groups who’ve held territory in Iraq and Syria.

The Pentagon confirmed that President Trump ordered the early Friday-morning attack that killed Soleimani, the head of the Islamic Revolutionary Guard Corps' elite Quds Force, among other military officials at Baghdad International Airport. The airstrike hit in Iraq.

An adviser to Iran's President Hassan Rouhani also quickly warned Trump of retaliation from Tehran.

"Trump through his gamble has dragged the U.S. into the most dangerous situation in the region," Hessameddin Ashena wrote on the social media app Telegram. "Whoever put his foot beyond the red line should be ready to face its consequences."

Compiled by Olalekan Adeleye

Fox News