Tunisia's top security official says 23 people have been arrested from the group suspected of being behind the museum attack that killed 21 people, but two Moroccan and one Algerian suspects are still at large.

Interior Minister Najem Gharsalli said Thursday the arrests included a woman and the group was connected to the al-Qaeda-linked Oqba Ibn Nafaa brigade.

The March 18 attack was claimed by an al-Qaida rival, the Islamic State group, but members of Oqba Ibn Nafaa have claimed allegiance to both radical groups.

The minister said at least 80 percent of the group behind the attack has been detained. He said the gunmen that attacked the museum carried belts filled with semtex explosive, which would have been "catastrophic" if used.