The US embassy in Qatar emailed US citizens in the Gulf country on Monday recommending that they shelter in place until further notice, triggering a slew of messages from various Doha-based institutions to employees and students while Qatar maintained that the situation was stable.
The British government later issued a warning recommending the same for UK citizens in the country.
The advice comes as Iran repeated earlier threats to retaliate against the United States after strikes on its nuclear sites.
The US and British messages noted that the recommendation was "out of an abundance of caution" and offered no further information.
Two US officials separately told Reuters that Iran could carry out attacks targeting American forces in the Middle East soon, with one source saying it could happen in the next day or two.
Commenting on the message, Qatari foreign ministry spokesperson Majed Al Ansari said in a statement that the security situation in the country remained stable, adding that the embassy's advisory did not suggest any specific threat.
Al Ansari said Qatar was ready to take all necessary measures to ensure the safety of its citizens and residents.
Qatar hosts Al Udeid Air Base, the largest US base in the Middle East, which serves as the forward headquarters for US Central Command and accommodates approximately 10,000 troops.
There was confusion among residents in Qatar over how to react to the mixed messages coming from the Qatari and embassy authorities on Monday afternoon.
The Qatar campuses of American universities offered differing advice to their staff and students, with Texas A&M University saying an evacuation of their building had been ordered, Northwestern University requesting that people go home and Georgetown University telling people they could go home if they wished.
The American School, which is not in session, closed its campus and cancelled summer camps until further notice.