Death toll rose to 39 in a beach resort and hotel attack in eastern Sousse city of Tunisia on Friday, said the Tunisian Interior Ministry.
The ministry added the number of casualties and injured could rise further.
Most of those killed in the attack were British, the Tunisian Prime Minister Habib Essid told a news conference on Saturday.
‘’After come the Germans, then the Belgians and then other nationalities," he said and added that French were also among the victims.
Rafik Chelli, Tunisian Interior Ministry secretary of state for security affairs, said the attack was organised by a university student from Kairouan city.
Photos of the incident surfaced on social media, showing several people in bathing suits, dead on the beach.
Following an exchange of gunfire, there were casualties, with one gunman shot dead by police, according to Reuters.
The unnamed official said the gunmen were armed with Kalashnikov assault rifles. Aside from the one attacker who was shot dead, it’s yet to be clarified how many other assailants took part in the attack.
The attack was on the Imperial Marhaba hotel, the source and local radio said.
Sousse is one of Tunisia's most popular beach resorts, drawing visitors from Europe and neighbouring North African countries.
Tunisia has been on high alert since March when militant gunmen attacked the Bardo museum in Tunis, killing a group of foreign tourists in one of the worst attacks in a decade in the North African country.
ISIS claimed the responsibility for the attack according to a statement on a Twitter account.