The Pakistani strikes overnight hit the capital Kabul and the city of Kandahar, where Taliban leaders are based.
It was the first time Islamabad has attacked the Taliban rather than militants allegedly backed by them, a stark rupture in ties between the Islamic neighbours.
Security sources in Pakistan said the strikes involved air-to-ground missile attacks on Taliban military offices and posts in Kabul, Kandahar as well as Paktia province.
There were ground clashes in multiple sectors along the border between the Islamic nations.
The Taliban said it launched what it described as retaliatory attacks on Pakistani military installations.
Both sides reported heavy losses.
"Our cup of patience has overflowed. Now it is open war between us and you (Afghanistan)," Pakistani Defence Minister Khawaja Muhammad Asif said on Friday.
The strikes threaten to unleash a protracted conflict along the 2600km frontier, with relations between Kabul and Islamabad shattered by a long-running dispute over Pakistan's accusation that Afghanistan harbours militants carrying out attacks across the border.
The Taliban have denied the charge and said Pakistan's security is an internal problem.
Pakistan is nuclear-armed and its military capabilities are vastly superior to Afghanistan, but the Taliban are adept at guerrilla warfare, hardened by decades of fighting with US-led forces, before returning to power in 2021.
Russia, China, Turkey and Saudi Arabia were trying to mediate, diplomats and news reports said.
Taliban spokesman Zabihullah Mujahid confirmed Pakistani forces carried out air strikes in parts of Kabul, Kandahar and Paktia but did not give details.
On Friday, the Taliban defence ministry said it "successfully conducted" air strikes using drones to hit military targets in Pakistan.
Pakistan's Information Minister Attaullah Tarar said the strikes were carried out by Pakistani Taliban militants and all the drones brought down by anti-drone systems with "no damage to life".
Mosharraf Zaidi, a Pakistani government spokesman, said in a post on X that the action was a response to "unprovoked Afghan attacks", adding 133 Afghan Taliban fighters were killed and more than 200 wounded, with 27 posts destroyed and nine captured.
Mujahid said 55 Pakistani soldiers were killed and 19 posts seized, while eight Taliban fighters were killed, 11 wounded and 13 civilians injured in Nangarhar province.
Clashes between Pakistan and Afghanistan in October killed dozens of soldiers until negotiations facilitated by Turkey, Qatar and Saudi Arabia brought an end to the hostilities.
Pakistan has been on high security alert since it launched air strikes earlier this week that Islamabad said targeted camps of Tehreek-e-Taliban, or Pakistani Taliban, and Islamic State militants in eastern Afghanistan.
Kabul and the United Nations said the strikes killed 13 civilians and reiterated it does not allow militants to operate from its territory.
The Taliban also warned there would be a strong response.
The government of Pakistan's Punjab province said it was on high alert for militant attacks on Friday and had conducted a series of security operations, taking 90 Afghan nationals to holding centres for deportation.
A state-run media outlet from Afghanistan's Nangarhar, Bakhtar News Agency, shared an image of what it said was a battalion of suicide attackers.
Pakistani officials have said in recent days they feared an escalation of militant strikes in urban centres.
with AP
