PORT AL KANTAOUI, Tunisia: Tunisia said Sunday it would deploy hundreds of armed police around tourist sites as authorities moved to ramp up security after a man gunned down 38 people at a seaside resort.

Police on horseback and quad bikes could be seen patrolling the beach at Port El Kantaoui where the attack, which was claimed by ISIS, took place Friday.

Tourists gathered around bouquets of flowers laid out in the sand, one marked with the message: “Why did they die?”

In Tunis, the National Security Council met to discuss what measures should be taken after the attack, which saw at least 15 Britons killed and dealt a heavy blow to the country’s vital tourism industry.

The Tourism Ministry confirmed plans to deploy 1,000 armed officers from July 1 to reinforce the country’s tourism police, who will also be armed for the first time.

Armed officers will be deployed “inside and outside hotels” as well as on beaches and at tourist and archaeological sites, the ministry said in a statement.

In a separate statement after the National Security Council meeting, President Beji Caid Essebsi stressed the need for “greater vigilance” and asked the government to consider “exceptional measures” to deal with future threats.

Authorities had previously announced plans to reinforce security at tourist sites and beaches, and to shut down 80 mosques accused of inciting extremism.

Investigators, meanwhile, are searching for one or more accomplices in the attack.

The father and three roommates of the attacker were detained and are being questioned in the capital, Tunis, Interior Ministry spokesman Mohammad Ali Aroui told the Associated Press. The attacker has been identified as Seifeddine Rezgui.

“We are sure that others helped, but did not participate,” Aroui said. “They participated indirectly.”

A security official close to the investigation confirmed news reports indicating that a swimmer had found the attacker’s cellphone in the Mediterranean. The phone showed the attacker spoke with his father just before his assault, the official said on condition of anonymity.

Authorities believe that the suspected accomplices provided the Kalashnikov assault rifle to Rezgui and helped him get to the scene, Aroui said.

The attack saw Rezgui pull out a Kalashnikov rifle hidden in a beach umbrella and open fire on holidaymakers at the Riu Imperial Marhaba hotel in Port El Kantaoui, near Sousse south of the capital Tunis.

Tunisian authorities have so far identified 18 of those killed as 14 Britons, a German, a Belgian, a woman from Ireland and another from Portugal.

The attack was Britain’s worst loss of life in a militant attack since the 2005 London bombings. Britain has said at least 15 of its citizens were confirmed dead and warned that the toll is likely to rise.

The British government cautioned Sunday that other attacks “are possible” in Tunisia, urging visitors to remain vigilant.

Tunisia has not yet published the full list of the victims’ names and their nationalities.

“We are taking the time we need. There must be zero errors. We have taken the dental and palm prints [of the victims]. Families have arrived from abroad to identify the bodies,” said Naoufel Somrani, head of the Health Ministry’s emergency services.

The attack was swiftly claimed by ISIS. It came just three months after another ISIS-claimed attack on the Bardo National Museum in Tunis killed 21 tourists and a policeman.

The tourism industry – which accounts for 7 percent of Tunisia’s GDP and almost 400,000 jobs – has been reeling since the 2011 revolution that ousted dictator Zine al-Abidine Ben Ali was followed by a rise in militant attacks.

Authorities had announced a nearly 26 percent drop in the number of foreign visitors in April compared with the same month last year.

There has been an exodus of shocked tourists since Friday’s attack, with British and Belgian tour operators saying they had flown out some 2,400 visitors by late Saturday. Hundreds more were expected to follow Sunday.

But some tourists said they had chosen to stay.

“It was nobody’s fault. We are scared ... But this kind of thing can happen anywhere,” French tourist Safia told AFP as she walked along a beach in the resort area.

In the past four years, dozens of police and soldiers have been killed in Tunisia in clashes and ambushes attributed to extremists – mainly in the western Chaambi Mountains.

While Tunisia has a tradition of secularism and a strong civil society, disillusionment and social exclusion have fuelled radicalism among young people, with the country exporting some 3,000 fighters to Iraq, Syria and neighboring Libya.