A third attacker is still "on the run" after the deadly Bardo Museum attack in which 23 people died, Tunisia's president said in a live TV interview.
"There were certainly three attackers... there is one who is on the run, he won't get far," President Beji Caid Essebsi said.
Suspects have been arrested over the attack but just two gunmen were thought to have assaulted the museum.
The news came after a video was released of the pair roaming the Bardo.
Mr Essebsi said it was clear there had been three attackers, because they had "been identified and filmed on surveillance cameras".
"We've asked the people to help [find the third attacker] because the people are interested in this."
He added in an interview with French media that a monument would be erected in memory of the victims.
Upsurge in extremism
The gunmen are said to have been trained in Libya in an area controlled by Islamic State (IS) militants.
IS has said it was behind the attack on the museum, which is situated next to the country's parliament.
The two gunmen seen in the video were named as Yassine Laabidi and Hatem Khachnaoui. They were both killed in a gunfight with security forces inside the building.
In an earlier interview with Paris Match, Mr Essebsi said that "shortcomings" in Tunisia's security system meant "the police and intelligence services had not been thorough enough in protecting the museum".
However, he added that the security services "reacted very efficiently" to the attack and had helped save dozens of lives.
Twenty foreigners were among those killed in the attack, including British, Japanese, French, Italian and Colombian tourists.
Following the attack, large numbers of Tunisians gathered outside the museum to protest against terrorism.
Tunisia has seen an upsurge in Islamist extremism since the 2011 revolution that ousted dictator Zine al-Abidine Ben Ali and sparked the Arab Spring.
The leader of Tunisia's moderate Islamist party, Ennadha, says the country will continue to be under threat of attack as long as neighbouring Libya remains unstable.
Rached Ghannouchi told the BBC that IS would not be able to establish a foothold in Tunisia itself but young men were being armed in Libya and crossing borders that were hard to control.
On Saturday, the brother of Yassine Laabidi, one of the gunmen, said Laabidi had been "brainwashed by swines who send young men to their death in the name of religion".
-BBC