Britain’s Foreign Office is advising British nationals to leave Tunisia, saying an additional terrorist attack is “highly likely.”

The warning comes after an attack at a beach hotel that left at least 38 people dead, most of whom were British citizens.

“If you’re in Tunisia and you don’t have an essential need to remain you should leave by commercial means,” read an updated advisory issued Thursday.

The ministry acknowledged additional security measures put in place by the Tunisian government since the attack, but it said they were insufficient to protect British tourists.

Over the weekend, Tunisian President Beji Caid Essebsi declared a 30-day state of emergency, giving the military and police more authority to combat terrorism and placing restrictions on such rights as public assembly.

That decision, too, was in response to the June 26 attack in which a gunman opened fire at the beachfront Hotel Riu Imperial Marhaba in the coastal city of Sousse.

“Terrorism is spreading,” Essebsi said. “I believe, and I say this plainly and clearly: If this were to happen, which happened in Sousse, if this were to happen again, the country would collapse.”

ISIS has claimed responsibility for the attack, but it is unclear whether the Islamist group had any direct role in it.