At least 14 Tunisian soldiers have been reported killed and 20 wounded after gunmen attacked military checkpoints near the Algerian border, the ministry of defence told Al Jazeera.
The fighters, one of whom was reported killed, staged two simultaneous attacks on army posts in the Mount Chaambi area as soldiers were holding their sundown meal, or Iftar, as part of the Ramadan Muslim fasting month.
They were armed with rocket-propelled grenades and rifles.
Thousands of Tunisian troops have been deployed in the area since April to counter fighters using the area since a French military operation drove al-Qaeda-affiliated fighters out of Mali last year.
"They attacked military checkpoints in Mount Chaambi, there are dead and wounded in this attack with RPGs and rifles," Rachid Hawela, a defence ministry spokesman told the Reuters news agency.
The attacks came nearly a year after Tunisian soldiers were ambushed in the same region.
Eight soldiers were killed in the attack on July 29 last year, several days after the assassination of opposition politician Mohamed Brahmi in Tunis.
Tunisian security officials say the numbers of fighters in the mountains are only in the dozens, but the government has struggled to combat the threat.
Last month, al-Qaeda in the Islamic Mahgreb, for the first time, claimed it carried out recent attacks in Tunisia, including an assault in May on the home of the interior minister that killed security guards.