Britain has advised its nationals in Tunisia to leave, warning local authorities could not provide "adequate protection" after last month's beach massacre that left 30 Britons dead.
"Although we have had good co-operation from the Tunisian government, including putting in place additional security measures, the intelligence and threat picture has developed considerably, reinforcing our view that a further terrorist attack is highly likely," the Foreign Office said on Thursday (local time).
"On balance, we do not believe the mitigation measures in place provide adequate protection for British tourists in Tunisia at the present time and we have therefore changed our travel advice accordingly."
The Foreign Office had previously advised against travel to certain hotspots, including near the borders with Algeria and Libya, but has now urged Britons to keep away from the whole of the country unless they have essential business.
It said that tour operators would be arranging additional flights to bring tourists home from Britain.
The warning comes almost a fortnight after a Tunisian student went on a rampage at a popular beach resort, killing 38 foreign tourists including 30 Britons. It was Britain's worst terror attack since the 2005 London bombings.
Tunisian President Beji Caid Essebsi on Saturday decreed a state of emergency in the north African country for 30 days, and Prime Minister Habib Essid said on Wednesday that the government feared more attacks.