All public consular operations have been suspended at the U.S. Embassy in Baghdad.

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Global powers are warning that the world has just become a more dangerous place as the US urges its citizens to leave the area "immediately" after the targeted killing by the U.S. of Iran’s top general.

The State Department posted a statement on its website and on Twitter urging citizens to leave Iraq and the closed US Embassy in Baghdad.

"U.S. citizens should depart via airline while possible, and failing that, to other countries via land," the statement read. "Due to Iranian-backed militia attacks at the U.S. Embassy compound, all public consular operations are suspended until further notice."

Iran vowed "harsh retaliation" for the airstrike near Baghdad's airport that killed Gen. Qassem Soleimani, the head of Iran's elite Quds Force.

The move marks a major escalation in the standoff between Washington and Iran. Iran's supreme leader warned that a "harsh retaliation is waiting" for the U.S. after the airstrike, calling Soleimani the "international face of resistance." Iranian president Hassan Rouhani said on Twitter "the great nation of Iran will take revenge for this heinous crime."