Reuters report that Tunisian security forces are surrounding the two militants, who are currently inside the museum.
Local reports say that 160 tourists have been rescued via a back door, while around 20 to 30 are still inside.
It is the first attack on a tourist site in years in Tunisia, a shaky young democracy that has struggled to keep Islamic extremist violence at bay.
It is not immediately clear who the attackers were, or if they took hostages.
Tunisia recently completed a rocky road to democracy after overthrowing its authoritarian president in 2011. It has been more stable than other countries in the region but it has struggled with violence by Islamic extremists in recent years, including some linked to Islamic State. It also has extremists linked to al Qaida’s North Africa arm who occasionally target Tunisian security forces.
Tunisia terror attack: 30 hostages believed to be held
