In its advice issued on 7 January, the embassy suggested citizens keep a low profile, be aware of their surroundings and remain especially alert in tourist locations, review their personal security plans and keep travel documents up to date and easily accessible.

Responding to a request from Delano, the embassy explained that it was a measure that had been taken by a number of US embassies.

“Our mission and our priority is the safety of all U.S. citizens abroad. Our U.S. embassies and consulates abroad issue Alerts as needed to notify U.S. citizens of safety and security concerns,” the embassy said in a statement on Tuesday.

US nationals travelling abroad can enroll in the smart traveler enrollment program STEP.State.gov to receive updates and monitor local media abroad. They can also check travel.state.gov for travel advisories and alerts in countries they plan to visit or where they reside overseas.

The response comes after the US military killed Iranian Major General Qasem Soleimani in an air strike on 3 January, prompting Iran’s supreme leader to warn “If you hit, you get hit back”. The following day (8 January) a Ukrainian passenger plane was shot down with a missile after taking off from Tehran, killing all 176 people on board. The Revolutionary Guards later admitted that the operator of a missile defence system had mistaken the aircraft for a US cruise missile and fired at it.