Pakistan summoned the most senior Afghan diplomat in the country on Tuesday to protest over border skirmishes that it said left five security personnel wounded and strained relations.
Exchanges of fire and ensuing protests are threatening to worsen already fractious ties between Kabul and Islamabad, despite renewed efforts last month by US Secretary of State John Kerry to get them to work more closely on peace efforts.
Cross-border clashes flared on Monday between Afghan and Pakistani security forces for the second time in five days with Kabul summoning the Pakistani charge d'affaires to protest the "unprovoked attack by Pakistani forces".
The war of words over the porous frontier continued Tuesday, with the foreign ministry in Islamabad summoning the Afghan charge d'affaires to warn against any repetition of what it too called "unprovoked firing".
Five members of the paramilitary Frontier Constabulary were wounded in the firing on Monday morning, the ministry statement said.
Both countries have blamed each other for starting the firing on the border, which is a crucial battleground in the fight against Taliban militants who operate in both countries.
The border is unmarked in places and a key battleground in the fight against Taliban violence plaguing both countries.
"The Afghan charge d'affaires was conveyed that in case of any further escalation as a result of this situation, the responsibility would be on the Afghan Government", the said statement.
Pakistan, which backed Afghanistan's 1996-2001 Taliban regime, is seen by the West as having a central role in negotiating a political settlement with Taliban insurgents who shelter in Pakistan's border districts.
But ties have worsened this year with the Afghan government accusing Pakistan of dropping its support for the peace process.