PESHAWAR: At least one Frontier Corps soldier was killed and two injured Thursday when unknown 'militants' attacked a security checkpost in Mohmand Agency, said security sources .

They said the militants were from Afghanistan and fled after retaliatory fire from law enforcers.

The injured soldiers were shifted to the Combined Military Hospital (CMH) Peshawar through a chopper.

Pakistan Army has been engaged in a grand operation, named "Zarb-i-Azb," against Taliban militants in the country's tribal areas following a Tehreek-i-Taliban Pakistan-claimed attack on Karachi in June last year.

In recent times, forces and the government have claimed that the unrest in border areas is a result of foreign interference, which has been blamed on Afghan and Indian spy agencies.

Afghanistan, on the other hand, blames Pakistan for not doing enough to curb terrorists, and accuses it of nurturing Taliban militants on its soil – a claim Pakistan has vehemently rejected.

Read: Ashraf Ghani slams Pakistan over recent Kabul attacks.

Pakistan has also dug out a 500 km trench along the porous Pak-Afghan border to stop the flow of weapons, militants and narcotics into Pakistan.

The width and depth of the trench is 10 feet by 10 feet, according to Major General Sher Afgan, the chief of Frontier Corps, who claims the trench helped security forces in stemming the flow of narcotics and weapons from Afghanistan into Pakistan.