PESHAWAR: At least four suspected militants were killed in a US drone strike in Nazyan district of Afghanistan's Nangarhar province, near Pakistan's Khyber Agency, sources said on Sunday.

Security sources said the the drone strike targeted a militant compound in the Nazyan district, killing four suspected militants.

Till 2014, Nazyan district had been serving as a safe haven for the Mullah Fazllullah led Tehreek-i-Taliban Pakistan (TTP).

According to security officials, militants based in the Nazyan district had planned the devastating attack on the Army Public School in Peshawar, which left over 140 children and teachers dead and scores injured.

Pakistani security forces also carried out ground offensives in Khyber Agency, particularly the Tirah Valley of Bara which borders Nazyan.

The forces cleared much of the Bara plain in Operation Khyber One launched in October 2014, while in a follow-on operation named Khyber-2, which ended in June 2015, cleared the fierce Tirah terrain consisting of deep valleys and high mountains.