Four arrested, military to patrol cities in Tunisian museum attack aftermath

The number of foreign tourists killed in Wednesday's attack on the national museum in Tunisia had also risen to 20

Tunisia said it would deploy the army to major cities and arrested four people on Thursday after militant gunmen killed 20 foreign tourists visiting the national Bardo museum, the worst attack on the north African country in more than a decade.

Japanese, Italian, Spanish and British visitors were among those killed when at least two militants opened fire on two tourist buses during a visit to the museum inside Tunisia's heavily guarded parliament compound.

Militants shot dead by security forces in the attack had been identified as Tunisians, Hatem al-Khashnawi and Yassin al-Abidi. Tunisia's Prime Minister Habib Essid said the latter had been under surveillance but "not for anything very special."

"We have identified them, it is indeed these two terrorists," the premier told French RTL radio. "Their affiliation is not clear at the moment."

The president's office said the army would be deployed. "After a meeting with the armed forces, the president has decided large cities will be secured by the army," a statement said.

The number of foreign tourists killed in Wednesday's attack on the national museum in Tunisia had also risen to 20 from 17 dead, Tunisia's health minister said on Thursday. Three Tunisians were also killed.

London said on Thursday a British woman was among the dead in what it called a cowardly and despicable "terrorist attack."

The assault -- the worst attack involving foreigners in the country since a 2002 suicide bombing in Djerba -- occurred at a sensitive moment time for Tunisia, just emerging from its often messy transition to full democracy.

Four years after a popular revolt toppled autocrat Zine El-Abidine Ben Ali, Tunisia has completed its transition to democracy with free elections, a new constitution and a compromise politics between secular and Islamist parties.

But security forces are battling against Islamist militants including Ansar al Sharia, which is listed as a terrorist group by Washington, and Okba Ibn Nafaa, a brigade of al Qaeda-affiliated fighters operating along the Algerian border.

The attack appeared squarely aimed at Tunisia's economy, with tourism accounting for seven percent of gross domestic product.

The local stock exchange dropped nearly 2.5 percent and two German tour operators said they were canceling trips from Tunisia's beach resorts to Tunis for a few days.

Accor, Europe's largest hotel group, said it had tightened security at its two hotels in Tunisia and Italy's Costa Cruises, a unit of Carnival Corp CCL.N, said on Thursday it had canceled stops in Tunisia. (Additional reporting by Mark John in Paris; writing by Patrick Markey; editing by Philippa Fletcher)