Tunisian President Beji Caid Essebsi denounced Monday's Islamist militants attacks on police and army posts near his country's border with Libya as "unprecedented" and coordinated assaults.
In statements broadcast on state television, Essebsi said the assault that killed 28 militants was "maybe aimed at controlling" the border region with Libya, and vowed to "exterminate these rats".
The attacks in the border town of Ben Guerdane, where 10 members of the security forces and seven civilians also lost their lives, were "unprecedented" and coordinated", said the president.
"Maybe they were aimed at controlling this region" in order to proclaim a "new (Islamist militant) province", he said.
"The Tunisian people are at war with this barbarism and with these rats and we will exterminate them... definitively," said Essebsi.
Tunisian forces fought off Monday's assailants in the second day of clashes in the border area in less than a week.
Tunisia has seen an emergence of radical Islam since the 2011 uprising that toppled longtime autocratic strongman Zine El Abidine Ben Ali who suppressed opponents including Islamists.
In recent years a large number of Tunisians have joined the Islamic State group (IS) in Libya, where authorities say they have been trained to carry out attacks at home.
Last year IS -- which has set up an Islamic "caliphate" in parts of Syria and Iraq under its control and is also active in Egypt -- claimed three attacks in Tunisia, killing dozens of foreign tourists and presidential guards.
Tunisia has been battling the militants who have taken advantage of a power vacuum in Libya -- also rocked by a 2011 uprising -- to set up bases, including in the Sabratha area between Tripoli and the border with Tunisia.