Tunisia is vowing a "strong and violent response" after suspected militants linked to al-Qaida killed four Tunisian police officers near the Algerian border.
About 20 rebels attacked security forces at a checkpoint in the country's mountainous Kasserine region overnight.
A Tunisian official attributed the shooting Wednesday to the Okba Ibn Nafaa Brigade, which was implicated in the killings of at least 14 Tunisian soldiers last year in the same area.
For two years, the Tunisian army has unsuccessfully attempted to push rebel fighters out of the mountains as it battles hardline Islamists who target security and government officials.
Earlier this month, a Tunisian official said authorities arrested 32 militants, some of them were returning from fighting in Syria and planning attacks in the country.
The Tunisian government of Prime Minister Habib Essid faces many challenges, including militant groups that surfaced in the country after a 2011 uprising that ousted former secular President Zine El Abidine Ben Ali.
Some material for this report came from AP, AFP and Reuters.