Tunisian authorities have arrested four people allegedly directly linked to Wednesday’s attack apparently targeting tourists at a museum that killed at least 21 people.
Five others suspected of having ties to the gunmen behind the raid, have also been detained, the presidency said in a statement.
Forty seven others were also reportedly injured in the shootings.
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 National Bardo 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.
Spain’s foreign minister said police searched all night for the pair, Juan Carlos Sanchez and Cristina Rubio.
A Japanese survivor described how she and her mother were shot in the hail of bullets.
“I was crouching down with my arms over my head, but I was shot in the ear, hand and neck,” 35-year-old Noriko Yuki said from her hospital bed in comments aired by Japanese broadcaster NHK.
“My mother beside me was shot in the neck. Mother couldn’t move by herself when the police came over,” she added.
Among the dead were three Japanese, four Italians, two Colombians and one each from Australia, France, Poland and Spain, Essid announced on television, in what he said was a definitive toll.
However, differing figures were given by other governments and there was conflicting information over the breakdown, with some of the dead identified as joint nationals.
The nationality of a 16th victim was not given, while the identity of the final fatality had not yet been established.
The Colombian tourists were a mother and child visiting Tunisia on a family holiday, their government said. The father survived the attack.
A Tunisian bus driver and a policeman were also reported dead in the attack on the Bardo, famed for its collection of ancient artefacts.
Al Jazeera’s Jacky Roland, reporting from Tunis, said there was a large police presence on the streets of the capital.
“We understand from the interior ministry that there may be other attackers or accomplices. It is believed there could be as many as three gunmen still out there.”
The attack appeared to be the worst on foreigners in Tunisia since an al-Qaeda suicide bombing of a synagogue killed 14 Germans, two French and five Tunisians on the island of Djerba in 2002.
It sparked outrage, with hundreds of people gathering later in a major thoroughfare of the capital, singing the national anthem and shouting slogans against the attackers, labelling them terrorists.
The assault also drew strong condemnation from world leaders, who vowed support for Tunisia.
US Secretary of State John Kerry denounced the “wanton violence” while British Prime Minister David Cameron said he was “appalled” by the attack and French President Francois Hollande expressed “solidarity” with the country.
United Nations Secretary-General Ban Ki-moon slammed the “deplorable” and “heinous” act and conveyed his “deepest sympathies” to the families of the victims.
Meanwhile the UN Security Council stressed that “no terrorist attack can reverse the path of Tunisia towards democracy”.
Tunisia has seen an upsurge in Islamist dissent since the 2011 revolution that ousted longtime strongman Zine El Abidine Ben Ali.
Dozens of police and military personnel have been killed or wounded in attacks blamed on armed groups. Al Jazeera