The US monitor of jihadist groups said late Thursday that the soldiers were killed in three blasts ignited by its fighters near Mount Mghila and that a "spy" was beheaded separately by IS.

The defence ministry announced the losses the same day, saying the soldiers in "a military unit tasked with carrying out a combing operation of Mount Mghila looking for terrorist elements were killed by a mine" explosion.

Mount Mghila, near the border with Algeria, is adjacent to Mount Chaambi, which is considered a hideout for jihadists.

Prime Minister Hichem Mechichi said the incident "will not stop us from pursuing our efforts to fight and defeat terrorism".

IS also said in its Al-Naba digital newspaper that jihadists executed a spy for the army on December 20 near Mount Selloum in the Kasserine region, also central Tunisia.

Authorities said at the time that the victim was a 20-year-old man named Oqba al-Dhibi, identified on local radio as a shepherd tending his flock when he was attacked.

Tunisia has seen a surge in radical Islam since veteran president Zine El Abidine Ben Ali was ousted in the country's 2011 revolution.

Dozens of members of the security forces have since been killed in jihadist attacks.

The army has been battling militants in the Kasserine area since 2012.

Tunisia's central mountains are also a hideout for a local branch of jihadist group Al-Qaeda in the Islamic Maghreb (AQIM).