The security forces also detained eight militants besides seizing weapons and ammunition and defusing 24 mines, it added.
The Afghan forces and some 100,000 NATO-led coalition troops have intensified operations against Taliban and other militants recently but the insurgents in retaliation responded by carrying out suicide attacks, roadside bombings and launching target killings.
Militants launched an armed attack killing a local elder in southern Helmand province, an official said earlier Monday.
"The armed militants opened fire against Abdul Samad, an influential elder and father of a senior provincial peace council official named Daud Farhang Sunday evening in Garmsir district," administrative chief of the district Ayub Omar told Xinhua.
Samad was transferred by security forces to a coalition hospital where he died of wounds late Sunday night.
No group claimed responsibility for the attack so far but the armed Taliban outfit, which launched spring offensive on May 3 this year, has said anyone working for the government and the NATO-led troops are legitimate target.