9 Arrested over Deadly Tunisia Museum Attack

"Security forces were able to arrest four people directly linked to the (terrorist) operation and five suspected of having ties to the cell," the presidency said in a statement on Thursday.

The Islamic State in Iraq and the Levant (ISIL) terrorist group has reportedly released audio recordings claiming responsibility over the attack at the National Bardo Museum.

Earlier on Thursday, officials identified two of the gunmen as Yassine Laabidi and Hatem Khachnaoui, saying one of the assailants was known to the intelligence services.

It was not clear which of the two men was known to the intelligence service and no formal links to a particular armed group had been established.

In an interview with France's RTL radio, Prime Minister Habib Essid said Tunisia was working with other countries to learn more about the attackers.

Both men were killed by security services in a raid after they attacked the museum.

Details about the attackers' identity emerged as President Beij Caid Essebsi vowed to wage a "merciless war against terrorism" after the gunmen killed 19 foreign tourists and two Tunisians in a daylight attack.

As the international community denounced Wednesday's assault, Essebsi said Tunisia would fight "to our last breath".

"I want the Tunisian people to understand that we are in a war against terrorism and that these savage minorities do not frighten us," said Essebsi, who visited some of the dozens being treated for wounds in a Tunis hospital.

The gunmen opened fire on the tourists - including visitors from Japan, Italy, France, Australia, Colombia, Poland and Spain - as they got off a bus then chased them inside the museum, said Prime Minister Habib Essid.

A Spanish man and a pregnant Spanish woman, who survived the attack by hiding in the museum all night in fear, were retrieved safely on Thursday morning by security forces, Tunisia's Health Minister Said Aidi told The Associated Press news agency.