An improvised explosive device killed four Tunisian soldiers patrolling a mountainous region near the Algerian border, Defense Ministry spokesman Mohammed Zekri said on Wednesday.
The mountainous Moghila area, near the poor town of Kasserine, is home to an Islamist militant group that the Tunisian army has been fighting for several years.
Tunisia is facing a small but persistent militant threat, say foreign diplomats with certainty.
In addition to jihadist cells being held in remote mountainous regions, which have not carried out successful strikes beyond their strongholds in recent years, there is also a threat from militants who have been radicalized online.
Last year, militants tried to attack the US embassy in Tunis, killing a police officer at a security guard wearing a suicide vest, and months later stabbed two security officers in a knife attack in the town of Sousse.
In October, a young Tunisian migrant arrived in France and immediately killed three people in a church.