At least five Pakistani soldiers have lost their lives in a series of assaults on several northwestern border posts by dozens of militants based in neighboring Afghanistan, security sources say.
A Pakistani security official said on Monday that the fighting took place in Mohmand, one of Pakistan's tribal districts where the military has been battling militants for over a decade.
"Dozens" of militants from across the border stormed security posts in Pakistan's Mohmand Agency on Sunday night, the unnamed official, who was based in the region, said.
Pakistan's military sources said 10 militants were also killed in the ensuing exchange of fire and fierce fighting.
Pakistani military Army chief General Qamar Javed Bajwa "hailed the sacrifices" of the Pakistan soldiers and called for greater numbers to man the border.
The Pakistani army's press wing said in a statement that Islamabad has also asked Afghan authorities to strengthen surveillance in border areas.
"Terrorists are common threat and must be denied freedom of movement/action along the border," the statement read.
Pakistan's Foreign Ministry summoned the deputy head of the Afghan embassy in Islamabad to lodge a "strong protest" over the deadly incident.
"The Afghan government was urged to thoroughly investigate the incidents and take firm action against the terrorists operating from its soil," the ministry said in a statement.
The latest militant raids came at a time of heightened tension between the Pakistan and Afghanistan. Islamabad blames Kabul for a recent string of militant attacks that killed 130 people across Pakistan in February.
Hundreds of Afghan families have been displaced due to cross-border shelling by Pakistani troops in recent weeks.
Afghanistan and Pakistan blame each other for the Taliban violence plaguing both countries.
The two neighbors have accused each other of allowing militants to shelter in the border regions and launch bloody attacks that threaten regional stability.