The ambush took place overnight in the northwestern Tirah valley in the Khyber agency, one of the main smuggling routes for arms and insurgents crossing between Afghanistan and Pakistan.
               
"Security forces ambushed (the) moving group ... Fleeing terrorists left behind bodies of their accomplices," the military said in a statement.
               
There was no independent verification of the clash.
               
The military also said late on Thursday that 17 militants were killed in air strikes in Khyber and 10 in ground fighting.
               
The army is fighting offensives against Pakistani Taliban insurgents in Khyber as well as the North Waziristan region, which is also on the Afghan border.
               
But the pace of operations has picked up since Pakistani Taliban suicide attackers killed 131 school children, nine teachers and a soldier at a military-run high school in the northwestern city of Peshawar on Tuesday.
               
The assault was the deadliest militant attack ever in Pakistan. Footage of terrified children and classrooms awash with blood has provoked a wave of revulsion in a country mostly inured to daily violence.
               
The Pakistani Taliban, who are allied with but separate from the Afghan Taliban, said the school attack was revenge for the offensive against them and they accused the military of killing civilians in remote areas where journalists are forbidden to go.
               
Many Pakistani militants have sought refuge from the offensive over the border in lawless areas of Afghanistan but they have come under attack there too, especially by missile-firing U.S. drones.
               
In the latest such attack, two militants were killed on Friday, just over the border from the Tirah valley, an Afghan official and militants said.
               
Since the school attack, the government has promised that Pakistan would not discriminate between different militant factions, trying to draw a line under years of support for some groups seen as useful in Pakistan's confrontation with India and in achieving Pakistan's aims in Afghanistan.
               
The government has also announced that it would rescind an unofficial moratorium on the death penalty.

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