TUNIS — The Islamic State jihadist group claimed responsibility for an attack on foreign tourists at Tunisia's national museum that killed 21 people, as the security forces swooped on suspects.
Authorities said they had identified the two gunmen killed after the Wednesday assault, prompting calls for a show of national unity against extremism in the birthplace of the Arab Spring.
In an audio message posted online on Thursday, IS said "two knights from the Islamic State... heavily armed with automatic weapons and grenades, targeted the Bardo Museum" in the capital.
The group, which has hundreds of Tunisians among its ranks, threatened more attacks, saying: "What you have seen is only the start."
Authorities say as many as 3,000 Tunisians have gone to Iraq, Syria and Libya to fight in jihadist ranks, raising fears of battle-hardened militants returning home to plot attacks.
The president's office said security forces arrested "four people directly linked to the (terrorist) operation and five suspected of having ties to the cell."
And a presidential source said soldiers were to be deployed in major cities following the assault, while insisting "we are not under siege".
As international outrage grew over Tunisia's worst post-revolution attack, President Beji Caid Essebsi said his country would not be cowed by extremism.
"The process of implementing a democratic system is underway, well anchored," he told France's TF1 television. "We will never move backwards."
The leader of the Islamist opposition party Ennahda, Rached Ghannouchi, said he was convinced that "the Tunisian people will stay united in the face of barbarity".
Panic broke out during the attack on Wednesday as gunmen in military uniforms opened fire at visitors as they got off a bus then chased them inside the museum.
The dead included three Japanese, two Spaniards, a Colombian, an Australian, a British woman, a Belgian woman, two French, a Pole and an Italian, Health Minister Said Aidi said.
Dozens more people were wounded in the assault, in a massive blow to Tunisia's heavily tourism-dependent economy.
After cowering in fear in the museum during the night, two Spanish tourists were discovered on Thursday alive and well, officials said.
At least two major cruise ship operators suspended stopovers in Tunis following the attack.
Nine of the slain tourists were from the MSC Splendida cruise ship, whose owners said a special psychology unit had been set up for passengers.
The government, in a show of defiance, said the National Bardo Museum would reopen early next week. — AFP