At least six Pakistani paramilitary soldiers and 12 Afghan civilians were killed in a clash with militants near the Afghan border, security officials told Reuters on Wednesday.
The clashes rupture a fragile peace that had briefly taken hold after weekend clashes between the countries killed dozens.
More than 12 civilians were killed in Afghanistan as fresh fighting broke out between Afghan and Pakistani forces on Wednesday, the Taliban said.
In an official statement, the Pakistani military claimed that it repulsed an attack along the Balochistan border on Wednesday, killing around 15 to 20 Afghan Taliban.
It did not mention civilian casualties.
Once allies, the recent friction between the South Asian nations erupted after Islamabad demanded that the Afghan Taliban administration act against militants who have stepped up attacks in Pakistan, saying they operate from havens in Afghanistan.
The Taliban denies the presence of Pakistani militants in Afghanistan.
