At least 14 Tunisian soldiers have been killed in a militant attack near the Algerian border with at least 20 others wounded, the defence ministry says.
They say gunmen, armed with rocket-propelled grenades and rifles, raided two checkpoints near Mount Chaambi.
It is reportedly the heaviest death toll registered by the army since independence in 1956.
The Tunisian army has been waging a crackdown on militants operating in the mountainous region over the past year.
Islamist militants, including fighters linked to al-Qaeda in the Islamic Mahgreb (AQIM), are believed to be hiding out in the border region.
The soldiers were attacked “by terrorist groups” on Wednesday evening as they were breaking their fast as part of the Muslim holy month of Ramadan, Tunisia’s Tap state news agency reports.
A group called the Okba Ben Nafaa Brigade has reportedly said it carried out the attack in a post on its Facebook page.
The office of the Tunisian presidency has declared three days of mourning starting on Thursday, Tunisian TV reports.
Eight soldiers were killed in an attack in the Mount Chaambi district in July 2013, days before the assassination of secular politician Mohamed Brahmi, which plunged the country into political turmoil.
Islamist militants have been increasingly active around the Algerian-Tunisian border since the 2011 Arab Spring uprising that toppled long-term leader Zine al-Abidine Ben Ali.