Gas-rich Qatar, which lies 190 kilometres (120 miles) south of Iran across the Gulf, is home to the US's largest military base in the region, Al Udeid.

"Out of an abundance of caution we recommend American citizens shelter in place until further notice," the US embassy said on its website.

Britain and Canada later cited the US security alert in their own recommendations to nationals.

Iran's armed forces threatened on Monday to inflict "serious, unpredictable consequences" on the US after its heavy strikes on three nuclear sites.

In Bahrain, a close neighbour of Qatar that hosts the US Fifth Fleet, the American embassy "temporarily shifted a portion of its employees to local telework", it said on X.

Bahraini authorities had already told most government employees to work from home until further notice, citing "regional circumstances".

Following the US warning in Doha, Qatar's foreign ministry spokesman Majed al-Ansari said warnings by foreign embassies "do not necessarily reflect the existence of specific or credible threats".

"We would like to reassure the public that the security situation in the state remains stable," he wrote on X. "Qatar continues to exert intensive diplomatic efforts to de-escalate tensions in the region."

On Sunday, the US State Department advised Americans worldwide to "exercise increased caution" because of the war between Israel and Iran.

After Israel's first strikes on Iran on June 13, the US embassy in Qatar had told its staff and other Americans to "exercise increased caution" and "limit non-essential travel to Al Udeid Air Base".

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