Hunt on for third Tunisian museum attacker

A third attacker is still "on the run" after the deadly Bardo Museum killings, Tunisia's president says.

A member of the Tunisian security services stands near the scene of an attack targeting tourists at the National Bardo Museum, Tunis, Tunisia, 18 March 2015. (EPA/MOHAMMED MESSARA)

A third attacker in the deadly assault on the Bardo museum is on the run, Tunisia's president says.

"There were certainly three attackers... there is one who is on the run, he won't get far," President Beji Caid Essebsi said on Sunday.

The Islamic State group claimed Wednesday's attack on foreign tourists in Tunis, the deadliest since Tunisia's 2011 revolution which sparked the Arab Spring regional uprisings.

Australian-Colombian dual national Javier Cameloan, 28, and his Colombian mother were among 21 people killed when two gunmen stormed the National Bardo Museum.

Essebsi said it was clear there had been three attackers, because they had "been identified and filmed on surveillance cameras".

Tunisia's Interior Ministry released security camera footage of Wednesday's attack showing two gunmen walking through the museum, carrying assault rifles and bags. At one point they encounter a third man with a backpack walking down a flight of stairs. They briefly acknowledge each other before walking in opposite directions.

Police responding to the attack shot and killed the two gunmen. They were identified as Tunisians in their 20s who had trained in Libya.

Essebsi said the extremists who have recruited about 3,000 Tunisians to fight in Iraq and Syria have no credible connection to Islamic belief. He said his country was at war with them.

"When war is brought upon us, we will wage war," he said.

Essebsi added that a monument would be erected in memory of the victims.