Nine people have been arrested in Tunisia in connection with Wednesday’s terror attack in the country’s capital, Fox News has reported.

Four of those arrested are suspected of being directly related to the attack, according to a statement released by Tunisia’s presidential office on Thursday. The other five were arrested "under strong suspicion of relation” to the shooting.

The attack at the Bardo National Museum in Tunis left 23 people dead, including tourists from Belgium, Colombia, France, Italy, Japan, Poland, Spain and the UK, according to Health Minister Said Aidi. 

More than 40 people, including tourists and Tunisians, were injured.

The attack began when two gunmen wearing military-style uniforms and wielding assault rifles opened fire on tourists getting off buses at the museum which is a landmark site in Tinisia. The attackers charged inside to take hostages before being killed in a firefight with security forces.

Police identified the attackers as Yassine Labidi and Hatem Khachnaoui, both of them Tunisians. No formal links to any particular terror group have been established, the AP reported.

Tunisia’s Prime Minister told French radio station RTL Labidi was flagged and monitored by the security services but wasn't being followed for anything special.

The announcement of the arrests by Tunisia’s presidential office came after a speech by President Beji Caid Essebsi late on Wednesday, in which he vowed to fight terrorism "without mercy" and said Tunisia was "in a war with terror."

No group has claimed responsibility for the attack.