A pitched battle between Tunisian forces and extremist attackers on March 7 left at least 53 people dead near Tunisia's border with Libya, the government said.
Tunisian Prime Minister Hassid Essid said on state television that the attack was an Islamic State (IS) attempt to carve out a stronghold on the border.
Gunmen attacked the city of Ben Guerdane at dawn on March 7 and fighting continued past nightfall, forcing Tunisia to close its border with Libya.
"This is an unprecedented attack, planned and organized. Its goal was probably to take control of this area and to announce a new emirate," Tunisian President Beji Caid Essebsi said.
The attack and ensuing fighting left 35 attackers, seven civilians, and 11 members of Tunisia's security forces dead, the government said.
Eyewitnesses said corpses lay in the street and gunmen hid in homes as darkness fell. Residents of Ben Guerdane said the gunmen spoke of creating a caliphate and "liberating" the town.
Tunisia, a relatively stable state in the volatile north Africa region, has repeatedly clashed with extremists on the borders with Libya and Algeria in recent years.
European Union foreign policy chief Federica Mogherini said the attack "once more demonstrates the gravity of the threat faced by Tunisia."
Based on reporting by AP, dpa, and AFP