Britons have been told not to travel to Tunisia unless it is essential as the Foreign Office changes its advice in the wake of the beach shootings.
It said people already in the country should leave "by commercial means" unless they definitely have to stay as further terror attacks are "highly likely."
Holiday companies are organising extra flights for their customers to leave.
And people who are travelling in Tunisia independently should made their own arrangements to leave.
They should contact the British embassy in Tunis if they need consular assistance.
38 tourists, including 30 Britons, were killed when a gunman opened fire on a beach and hotel resort in Port El Kantaoui, near Sousse on 26 June.
In a statement, the Foreign Office said: "Further terrorist attacks are highly likely, including in tourist resorts, and by individuals unknown to the authorities whose actions may be inspired by terrorist groups via social media.
"You should be especially vigilant at this time and follow the advice of the Tunisian security authorities and your tour operator, if you have one."
