Britain has suspended embassy operations in Kuwait City and urged UK businesses there to review security measures due to a terror threat.
It comes less than two weeks before a planned visit to the country by the Prince of Wales to mark the 50th anniversary of its independence.
"We are aware of an increased terrorist threat against the British Embassy in Kuwait," a spokeswoman said, but she declined to comment on whether it was linked to the royal visit.
"We have therefore taken the precaution of temporarily suspending embassy services."
All non-essential staff have been sent home.
In a wider caution to Britons in the country, she said: "We cannot rule out the threat against other British interests in Kuwait, and have therefore urged British business and organisations to review their own security procedures."
Charles is scheduled to make a short visit to the Middle East on October 31 and November 1 en route to Africa.
He will go to Kuwait to celebrate the 50th anniversary of independence as the guest of the Amir and the Crown Prince, and will then stop briefly in Qatar for discussions with the Emir.