Iranian Ambassador to the United Nations Majid Takht Ravanchi told the CNN broadcaster in an interview that the United States “started a military war” against the Islamic Republic by killing Qasem Soleimani, the commander of the Iranian Islamic Revolutionary Guard Corps’ elite Quds Force.

“Last night, they [the United States] started a military war by assassinating, by an act of terror against one of our top generals. So what else can be expected of Iran to do? We cannot just remain silent. We have to act and we will act”, Ravanchi said.

Echoing Khamenei, the Iranian ambassador to the United Nations also promised that the United States would face revenge for the assassination.

“The response for a military action is a military action. By whom? When? Where? That’s for the future to witness”, Ravanchi added.

In the earlier hours of Friday, Soleimani was killed by a US drone attack near the Baghdad International Airport.

US President Donald Trump said Washington took preemptive action against Soleimani to “stop a war.” An adviser to Iranian President Hassan Rouhani, however, said the United States crossed a “red line” with the attack, while Iran's supreme leader Ali Khamenei warned that a “harsh retaliation is waiting” for the United States.

The Friday strikes also killed Iraqi Shiite militia commander Abu Mahdi al-Muhandis and 10 other people. 

Tensions are high across the Middle East after the United States killed Soleimani in an airstrike on the outskirts of Baghdad. The US Embassy in Baghdad on Friday called on US citizens to depart Iraq as soon as possible.

Iran’s National Security Council said in a statement it will respond to Soleimani's death "at the right time and in the right place".