The United States has conducted a military operation that killed an Iranian military chief and a leader of an armed Iraqi group.

The Pentagon, U.S. military headquarters, confirmed in a statement that Qasem Soleimani, the leader of Iran’s elite Quds Force unit of the Iranian Revolutionary Guard Corps, was killed in an airstrike at the Baghdad International Airport, Iraq.

Abu Mahdi al-Muhandis, the leader of Kata’ib Hezbollah, also called Popular Mobilisation Forces (PMF) in Iraq, was also killed in the strike. The PMF is an Iraqi paramilitary group that carried out a violent protest at the U.S. Embassy in Baghdad on December 31, 2019. The group is also embedded in the Iraqi military and Iraq has officially condemned his killing warning it could escalate tensions in the country.

The Pentagon said President Donald Trump ordered the military operation that killed both targets, saying they were both linked to the attempt to storm the embassy.

“At the direction of the President, the U.S. military has taken decisive defensive action to protect U.S. personnel abroad by killing Qasem Soleimani, the head of the Iranian Revolutionary Guard Corps-Quds Force, a U.S.-designated Foreign Terrorist Organization,” the Pentagon statement said circulated on Twitter Friday morning.

The Pentagon also said Mr Soleimani “was actively developing plans to attack American diplomats and service members in Iraq and throughout the region.”

“He was responsible for the deaths of hundreds of American and coalition service members and wounding of thousands more,” the statement said, noting further that the operation was aimed at serving as a deterrence to further attacks on American interests.

The state television in Iraq was the first to announce that Messrs Soleimani and Muhandis had been killed in the airstrike.

The strike followed several warnings from American authorities that there would be harsh consequences for the Tuesday’s violent protest at the embassy in Iraq. President Donald Trump threatened to deal with Iranians involved, while other military chiefs and diplomats also threatened similar actions.

Mr Trump has not personally commented on the airstrike, but he tweeted the American flag Friday morning.

Ayatollah Khamenei, the Iranian supreme leader, called Mr Trump’s bluff in a January 1 tweet, saying the American president cannot do anything.

That guy has tweeted that we see Iran responsible for the events in Baghdad & we will respond to Iran.
1st: You can’t do anything.
2nd: If you were logical —which you’re not— you’d see that your crimes in Iraq, Afghanistan… have made nations hate you. https://t.co/hMGOEDwHuY

— Khamenei.ir (@khamenei_ir) January 1, 2020

The supreme leader said in a Friday morning tweet that Mr Soleimani was a martyr, mourning his death in the hands of Americans as barbaric.

That guy has tweeted that we see Iran responsible for the events in Baghdad & we will respond to Iran.
1st: You can’t do anything.
2nd: If you were logical —which you’re not— you’d see that your crimes in Iraq, Afghanistan… have made nations hate you. https://t.co/hMGOEDwHuY

— Khamenei.ir (@khamenei_ir) January 1, 2020

Mr Khamenei on state television also vowed that “a harsh retaliation is waiting” and announced three-day mourning across Iran.

Iranian Defence Minister Amir Hatami was also quoted by the state news agency IRNA as saying Iran will take a crushing revenge for the killing which Iran described as an assassination.

“A crushing revenge will be taken for Soleimani’s unjust assassination … We will take revenge from all those involved and responsible for his assassination,” Mr Hatami said.

Considering his top role in Iran, Mr Soleimani’s death could escalate tensions in the Middle East. His Quds Force, which operates as an intelligence arm of Iran’s Revolutionary Guard Corps, has long been accused of providing support to groups throughout the Middle East, especially Hezbollah, Hamas, and other radical militias.