The Taliban government has confirmed that it attacked Pakistani troops in multiple mountainous locations on the northern border.
Casualties are not yet clear in what the Taliban called "retaliatory operations", after it said Pakistan violated Afghan airspace and bombed a market inside its border on Thursday.
Pakistani Interior Minister Mohsin Naqvi called the Taliban attacks "unprovoked", accusing them of firing at civilians. Pakistani forces would respond "with a stone for every brick", he warned.
Islamabad accuses Kabul of harbouring terrorists who target Pakistan on its soil, a claim the Taliban reject. The escalation came as the Afghan Taliban foreign minister was in India for an historic visit.
Both sides are said to have used small arms and artillery in the Kunar-Kurram region, the BBC understands.
