Air strikes by fighter jets meanwhile killed up to 15 militants in a border tribal district where the military began a major offensive earlier this year.
Troops recovered the eight corpses late Tuesday after they were spotted by local residents in the Khyber tribal district, where Taliban and Lashkar-e-Islam fighters are based.
Five bodies were recovered from one place and three from another, a senior government official in Khyber told AFP on condition of anonymity.
A second official in Khyber confirmed the recovery.
The army launched a fresh offensive in Khyber district this year against militant group Lashkar-e-Islam, led by warlord Mangal Bagh who has joined hands with the homegrown Tehreek-e-Taliban Pakistan.
Neither the military nor rival militants claimed the killings. But troops have in the past been accused of the extra-judicial killing of captured militants in the region.
Retired brigadier Mahmood Shah, a former security chief for the tribal areas, told AFP the deaths could also be a result of infighting among militant groups.
Separately, 15 militants were killed on Wednesday as jets hit their hideouts in North Waziristan tribal district, the military said in a statement.
An intelligence official told AFP the planes bombed a meeting place for insurgents in Datta Khel village, and said the dead included six Arabs and seven Uzbeks.
It was not possible to independently verify the casualties.
Pakistan’s semi-autonomous areas have long been a hideout for Islamist militants of all stripes — including Al-Qaeda and TTP as well as foreign fighters.
Pakistani jets and artillery began targeting rebel strongholds in North Waziristan in mid-June and ground forces moved in on June 30.
The army says it has killed more than 1,100 militants and lost more than 100 soldiers since then.
An AFP tally based on regular updates from the military puts the militant death toll at more than 1,500, with 125 soldiers killed. -AFP