Iran’s supreme leader Ayatollah Ali Khamenei vowed “severe revenge” after the United States killed the commander of the Islamic republic’s Quds Force, General Qasem Soleimani, in Baghdad on Friday.

“Martyrdom was the reward for his ceaseless efforts in all these years,” Khamenei said on his Farsi-language Twitter account in reference to Soleimani.

The leader has also declared a three-day mourning.

“With him gone, God willing, his work and his path will not be stopped, but severe revenge awaits the criminals who bloodied their foul hands with his blood and other martyrs” in last night’s incident,” he added.

Iranian foreign minister Mohammad Javad Zarif also lashed out at the United States for carrying out airstrikes at the Baghdad International Airport, killing the top commander.

The foreign minister termed the US decision to carry out the attacks as an “act of international terrorism”, adding that it was an “extremely dangerous and foolish escalation”.

“US’ act of international terrorism, assassinating General Soleimani — the most effective force fighting Daesh (ISIS), Al Nusrah, Al Qaeda — is extremely dangerous and foolish escalation,” he said.

He further said that the US “bears responsibility for all consequences of rogue adventurism”.

Pentagon officials on Friday confirmed that at the direction of US President Donald Trump, the military had taken the “decisive defensive action to protect US personnel abroad” by killing Qasem Soleimani, the head of Iran’s Islamic Revolutionary Guard Corps’ (IRGC) elite Quds Force.

It said that General Soleimani was “actively developing plans to attack American diplomats and service members in Iraq and throughout the region”.

“The strike was aimed at deterring future Iranian attack plans… The US will continue to take all necessary action to protect our people and our interests wherever they are around the world,” it added.

Soleimani was among the eight people who were killed in a rocket attack by the US on Baghdad international airport. The rocket attack comes days after a pro-Iran mob laid siege to the American embassy.

The IRGC said that Abu Mahdi al-Muhandis, the second-in-command of the Hashd Shaabi or the Iraqi Popular Mobilization Forces (PMF), was also killed along with Soleimani in the strike that targeted their vehicle on the Baghdad International Airport road.