Iran's supreme leader Ali Khamenei warned on Friday that “a harsh retaliation is waiting” after a US airstrike killed Quds Force Commander Gen. Qassem Soleimani in Baghdad.
Khamenei called for a three-day mourning and said Soleimani's killing will double the motivation of the resistance against the US and Israel.
Iran will be more determined to resist the US, President Hassan Rouhani said, Iranian state television reported.
"Soleimani's martyrdom will make Iran more decisive to resist America's expansionism and to defend our Islamic values. With no doubt, Iran and other freedom-seeking countries in the region will take his revenge," said Rouhani in a statement.
Iran's foreign minister, Mohammad Javad Zarif, slammed the killing as a dangerous escalation and warned Washington would bear responsibility for the consequences.
"The US' act of international terrorism, targeting and assassinating General Soleimani... is extremely dangerous and a foolish escalation," Zarif wrote on Twitter.
"The US bears responsibility for all consequences of its rogue adventurism," he added.
Defense Minister Amir Hatami said Iran will take a crushing revenge, according to state news agency IRNA.
"A crushing revenge will be taken for Soleimani's unjust assassination ... We will take revenge from all those involved and responsible for his assassination," Hatami said.
According to The Pentagon, US President Donald Trump ordered Soleimani's "killing" after a pro-Iran mob this week laid siege to the US embassy.
Following Soleimani's death, Trump tweeted an image of the US flag without any further explanation.
Early Friday, a volley of missiles hit Baghdad's international airport, striking a convoy belonging to the Popular Mobilization Forces (PMF).
Just a few hours later, Iranian state television carried a statement by the Revolutionary Guard Corps saying Soleimani "was martyred in an attack by America on Baghdad airport this morning."
An adviser to Iran's supreme leader threatened US troops in the Middle East and said “this is the time to clear the region from these insidious beasts.”
Ahmad Khatami made the comment while leading Friday prayers in Tehran. The hard-liner said Americans will never enjoy peace of mind again.
“I am telling Americans, especially Trump, we will take a revenge that will change their daylight into a nighttime darkness.”