Local radio added that the attack took place around midnight and the militants fled with the guardsmen's weapons.The attack took place near Mount Chaambi, a national park on the Algerian border that has provided refuge to Al-Qaeda linked Islamist radicals blamed for attacks against army and politicians in Tunisia for the past two years.

The attack comes as Tunisian forces on the Libyan border are on high alert in the wake of the murder of 21 Egyptian Christians in Libya by another radical Islamic group. Tunisia is also bracing for an influx of Egyptians fleeing Libya.

Since Tunisians overthrew their secular dictator in 2011, kicking off the region-wide Arab Spring, they have come increasingly under attack by Islamic militants.Despite the efforts of Tunisia's small army, attacks have continued around Mount Chaambi near the city of Kasserine. 

The militants in the area are believed to be part of the Oqba bin Nafaa radical group, the military wing of Ansar al-Sharia, whose leaders fled to Libya in 2013.Algerian and Tunisian forces are attempting to coordinate their efforts to control the rugged region, which straddles the border between the two countries.

On Monday, Algerian forces killed a militant carrying explosives near Tebessa, just across the border from Kasserine.