The Afghan Taliban says it has responded with renewed attacks against Pakistani troops along their shared border. BBC reported.
Pakistani authorities said that their "counter strikes" on the Afghan cities were a response to "unprovoked Afghan attacks" - though the Afghan Taliban said those were in response to earlier Pakistani strikes.
The two countries agreed a fragile ceasefire in October after deadly cross-border clashes, but fighting has flared once again in recent days.
Residents in Kabul heard loud blasts across the city on Friday, AFP reported.
Both sides claim to have inflicted heavy losses on each other during recent clashes. People in Pakistan's border regions told the BBC they had heard explosions and were asked to move to safety.
Pakistan earlier said that two of its soldiers have been killed after the Afghan Taliban launched an operation against military positions along their shared border late on Thursday.
Three others were injured as Pakistani forces responded to the "unprovoked fire", Information Minister Attaullah Tarar said.
The Afghan Taliban said it had launched the "large-scale" operation in response to strikes earlier this week, which it claimed had killed at least 18 people. Islamabad said it had targeted alleged militant camps and hideouts.
Taliban military spokesman Mawlawi Wahidullah Mohammadi said the "retaliatory operation" had been launched at around 20:00 local time (15:30 GMT) on Thursday.
The group's chief spokesman Zabihullah Mujahid said the offensive had killed "numerous" Pakistani soldiers and captured others.
This was denied by a spokesman for Pakistan's prime minister, who also contested Mujahid's claim that 15 military posts had been captured.
Prime Minister Shehbaz Sharif's spokesman Mosharraf Zaidi dismissed claims of damage on the Pakistani side and said all aggression would receive an "immediate and effective" response.
