TheIslamic State militant grouphas claimed responsibility for an attack on a museum in the Tunisian capital on Wednesday which killed 20 foreign tourists, according to an audio recording distributed online.
It praised the two attackers whom the recording said were "knights of the Islamic State" who were armed with machineguns and bombs.
Tunisian army to increase security after museum attack
Tunisia said it would deploy the army to major cities and arrested nine 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.
The assault -- the worst attack involving foreigners in Tunisia since a 2002 suicide bombing in Djerba -- came at a fragile moment for a country just emerging to full democracy after its Arab Spring uprising four years ago.
It is heavily reliant on foreign tourists to its beach resorts and desert treks, and the government was about to tackle politically sensitive reforms aimed at boosting economic growth.
There was no immediate claim of responsibility, but such an attack had long been feared. Tunisians make up the one of the largest contingents of foreign fighters in Syria, Iraq and Libya and their homeland's young democracy was a clear potential target.
The two militants shot dead by security forces in the Bardo attack had been identified as Tunisians, Hatem al-Khashnawi and Yassin al-Abidi. Two local newspapers reported Abidi had spent time in Iraq and Libya, but officials did not confirm that.
Tunisia's Prime Minister Habib Essid said Abidi 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."
Authorities said they had arrested four people directly linked to the attack and five others with indirect ties.
Tunisian forces had already cracked down on militants who emerged after the 2011 revolt. But Islamic State fighters are gaining ground in the chaos in neighboring Libya and Tunisian nationals are prominent in their ranks.
The president's office said the army would be deployed to the streets as part of increased security following the attack. "After a meeting with the armed forces, the president has decided large cities will be secured by the army," it said.
The number of foreign tourists killed rose to 20 from 17, the health minister said. Three Tunisians were also killed.
London said on Thursday a British woman was among the dead in an incident it said was cowardly and despicable.
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 compromise politics between secular and Islamist parties.
But security forces are battling 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 in the Chaambi mountains along the Algerian border.
The fight against these militants may have played a role in prompting the museum attack, said Geoff Porter, security analyst at North Africa Risk Consulting. "Increasing pressure on terrorist activities in the Djebel Chaambi region may have squeezed the balloon, with terrorists seeking softer targets with more symbolic impact," he said.
One former commander in Tunisia's Ansar al Sharia was killed last week fighting for Islamic State in Libyan city of Sirte. He had been running training and logistics, security sources said.
Tunisian and foreign security services on Thursday were still piecing together whether the two young Tunisian militants were associated with Islamic State or an Al Qaeda in the Islamic Maghreb affiliated group.
Poland's Foreign minister Grzegorz Schetyna told local radio that there were signs that the attackers were linked to Islamic State militants, but he gave no details.
A daily Islamic State news broadcast distributed online also mentioned the Tunis attack, describing the perpetrators as Mujahideen and asking God to receive them as martyrs in paradise. But it did not claim direct responsibility.
A social media account linked to Okba Ibn Nafaa brigade also provided details of the attack, without a direct claim of responsibility. But that group has also issued conflicting statements in the past about its position on Islamic State.
The Bardo attack appeared squarely aimed at Tunisia's economy, with tourism accounting for seven percent of gross domestic product. The government estimates that loses this season for the tourism sector would reach $700 million.
Two German tour operators said they were cancelling trips from Tunisia's beach resorts to Tunis for a few days and Accor, Europe’s largest hotel group, said it had tightened security at its two hotels in Tunisia. Italy's Costa Cruises, a unit of Carnival Corp, canceled stops in Tunisia.