The Pakistani army says it is searching for dozens of soldiers missing after their checkpoint on the Afghan border was attacked by the Taliban on Monday.
The Afghan Taliban said on Wednesday that it was holding up to 40 Pakistani troops after the raid in the Mohmand tribal area.
"We are looking for them," Pakistani army spokesman Athar Abbas said.
Maj Gen Abbas confirmed 40 Frontier Corps troops were missing and every effort was being made to find them.
A senior security official in Mohmand tribal region told the BBC Urdu service that contact was lost with the missing soldiers after the attack on Monday by the Afghan Taliban in the Shonkarai area of Mohmand.
"Ten of the missing soldiers subsequently returned to their positions the same day, but about 40 are still missing," he said.
Meanwhile, Afghan military commander Gen Mohammad Afzal - based in the border province of Kunar - told the BBC that clashes have erupted between the Taliban and Pakistani border forces in the Mohmand and Bajaur areas for the the last five or six days.
Gen Afzal said that during this period, Pakistani soldiers mistakenly crossed into Afghan territory twice to seek shelter with local people.
He confirmed reports from Wednesday that between eight and 10 soldiers had been handed over to Pakistani consulate in the nearby city of Jalalabad.
The BBC's M Ilyas Khan says that while attacks by the Taliban on border check posts are relatively routine, it is unusual for Pakistani soldiers to be held by the militants in Afghanistan.
A Taliban spokesman told the BBC on Wednesday that it was in fact holding Pakistani troops on both sides of the border after Monday's attack.
It said 30 soldiers were being held in Afghanistan and 10 in Pakistan after the checkpoint was overrun.
In the latest clashes in the area on Wednesday, the army said that 10 soldiers and 63 militants had been killed in fighting 20km (12 miles) from the border post.
"It was fierce fighting. We also sought air support to target militants' positions," Frontier Corps spokesman Maj Fazal-ur-Rehman told the Reuters news agency.