Videos shared by Afghan security forces showed Humvees driving through dark, mountainous terrain at night, lit by flashes of gunfire. Sustained bursts of automatic fire could be heard in the background.
Reuters could not independently verify the location, timing or authenticity of the images.
Pakistan was responding to "unprovoked fire" by Afghan forces along the border, the Information Ministry in Islamabad said subsequently on Thursday.
Afghan forces opened fire on posts in Pakistan's mountainous northwest, sparking more than two hours of fighting before Pakistani troops retaliated, Pakistani officials said, speaking on condition of anonymity as they were not authorised to speak to the media.
Pakistan's information ministry wrote on X that Pakistani troops delivered an "immediate and effective response", inflicting heavy casualties and destroying multiple posts and equipment.
The clashes along the 2600 km border, known as the Durand Line, are the latest flare-up to threaten a fragile ceasefire following deadly clashes in October.
A Qatari-mediated ceasefire between the two countries has largely held, but the two sides have still occasionally traded fire across the border. Several rounds of peace talks in November failed to produce a formal agreement.
On Sunday, Pakistan's military carried out strikes along the border with Afghanistan, saying it had killed at least 70 militants from Tehreek-e-Taliban Pakistan (TTP) and Islamic State in Khorasan Province in eastern Afghanistan.
Afghanistan rejected the claim, saying dozens of civilians had been killed, including women and children. The Defence Ministry said "various civilian areas" in eastern Afghanistan had been hit, including a religious madrassa and several homes. The ministry said the strikes were a violation of Afghanistan's airspace and sovereignty.
Islamabad says TTP leaders operate from Afghan territory and use it as a safe haven to plan attacks inside Pakistan, a charge Kabul denies.
"In response to repeated provocations and violations by Pakistani military circles, large-scale offensive operations have been launched against Pakistani military positions and installations along the Durand Line," the spokesperson for Afghanistan's Taliban administration, Zabihullah Mujahid, said in a post on X.
"Specialised laser units have also begun operations along the Durand Line, which would take advantage of the darkness of night", Mujahid said in a separate statement.
Pakistan said it was boosting security nationwide this week, placing forces on "high alert" and accelerating intelligence-based operations, arresting dozens of suspected militants, their handlers and facilitators, including Afghan nationals.
with AP
