A Tunisian soldier was killed and five others wounded Friday by a mine in the Mount Chaambi region near the Algerian border, the defence ministry said.
Since late 2012, security forces have been battling jihadist militants accused of having links to Al-Qaeda who are hiding out in the region, just a few kilometres (miles) from the Algerian border.
More than 20 police and troops have been killed in the area, many by improvised bombs and mines, since the beginning of the unrest, including eight soldiers killed in an ambush last July.
"A mine exploded when a military vehicle passed," killing a senior non-commissioned officer and wounding five other soldiers, two of them seriously, ministry spokesman Taoufik Rahmouni said on Friday.
Despite the regular use of aerial and artillery in the region, the security forces have failed to track down and eliminate the militants.
"It is impossible to gain 100 per cent control over an area of this terrain and this size," Rahmouni said.
Last month, the authorities designated Mount Chaambi and neighbouring mountain districts a closed military zone, and warned of the growing threat posed by "terrorist organisations" based in them.
President Moncef Marzouki has also offered an amnesty to any jihadists who hand over their weapons and who are not guilty of murder.