Islamabad, Nov 26 (IANS): At least 20 Pakistani soldiers were killed and four wounded as NATO helicopters from Afghanistan carried out an "unprovoked" attack on a border post early Saturday, the Geo News quoted Pakistani military as stating.

According to a military spokesman, NATO helicopters carried out indiscriminate and unprovoked firing on the Pakistani checkpost in Mohmand agency last night.

Mohmand agency is a district in Pakistan's Federally Administered Tribal Areas of Pakistan (FATA).

The attack was carried out on the Salala checkpost in Baizai district, said security officials in the Mohmand tribal region near the Afghan border and a military official in Peshawar, adding that at least 20 troops including two officers were killed in the pre-dawn incident.

Later, while admitting being aware of "an incident" near the border, the NATO said, it was investigating it.

Following the airstrike, Pakistani security forces sealed Mohmand Agency's all entry and exit points.