BAGHDAD: Iran has vowed “harsh retaliation” for a U.S. airstrike near Baghdad’s airport that killed Tehran’s top general and the architect of its interventions across the Middle East, as tensions soared in the wake of the targeted killing.

The killing of Gen. Qassem Soleimani, the head of Iran’s elite Quds Force, marks a major escalation in the standoff between Washington and Iran, which has careened from one crisis to another since President Donald Trump withdrew from the 2015 nuclear deal and imposed crippling sanctions.

The United States urged its U.S. citizens to leave Iraq “immediately.”

The State Department said the embassy in Baghdad, which was attacked by Iran-backed militiamen and other protesters earlier this week, is closed and all consular services have been suspended.

Around 5,200 American troops are based in Iraq, where they mainly train Iraqi forces and help to combat Islamic State militants.

Iran’s Supreme Leader Ayatollah Ali Khamenei warned that a “harsh retaliation is waiting” for the U.S. after the airstrike, calling Soleimani the “international face of resistance.”

Khamenei declared three days of public mourning for the general’s death, and appointed Maj. Gen. Esmail Ghaani, Soleimani’s deputy, to replace him as head of the elite Quds force.

Iran also summoned the Swiss charges d’affaires, who represents U.S. interests in Tehran, to protest the killing. Iran’s Foreign Minister Mohammad Javad Zarif called the strike “an act of state terrorism and violation of Iraq’s sovereignty.”

The killing, and any forceful retaliation by Iran, could ignite a conflict that engulfs the whole region, endangering U.S. troops in Iraq, Syria and beyond.

Over the last two decades, Soleimani had assembled a network of heavily armed allies stretching all the way to southern Lebanon, on Israel’s doorstep.

(Agencies)