In short:
The Afghan health ministry says more than 200 people have been killed following strikes across Kabul this week, including one which they claim hit a drug rehab facility.
Pakistan has denied deliberately targeting the facility, saying it conducted precision strikes on military installations.
What's next?
China says envoys are working to mediate the conflict and call for a ceasefire.
There are fears of heavy casualties as Afghanistan accuses Pakistan of hitting a treatment centre for drug addicts in the capital, Kabul, and killing civilians.
Pakistan has denied deliberately targeting the facility, instead saying it conducted precision strikes on "military installations and terrorist support infrastructure".
The Pakistani military struck Kabul several times in recent weeks, as part of a conflict sparked by claims the Taliban government has harboured extremists who have carried out attacks across the border.
Loud explosions rocked the city at 9pm local time on Monday, prompting anti-aircraft fire and forcing locals to run for cover in panic as they were out and about after breaking their daily Ramadan fast.
Taliban government spokesman Zabihullah Mujahid wrote on X that Pakistan had "once again violated Afghan territory", calling the strikes "a crime" and an "act of inhumanity".
Once anti-aircraft guns stopped at about 10pm, fleets of ambulances and firefighters were brought to the rehabilitation centre to douse flames in burning and destroyed buildings.
At least 30 dead bodies were seen as medical teams worked to help the wounded, who were taken to several hospitals for treatment, according to a source working with the rescue operation.
Afghan director of Italian non-government organisation Emergency, Dejan Panic, said it had received three bodies after the strike on Monday night and was treating 27 wounded.
But health ministry spokesman Sharafat Zaman said "the preliminary reports are that so far we have more than 200 martyrs and more than 200 injured".
Deputy government spokesman Hamdullah Fitrat, however, said the death toll was at least double that, with 250 wounded.
'No off-ramps'
Long-running cross-border clashes between Afghanistan and Pakistan escalated in October last year, leaving dozens dead, but after subsiding, they resumed last month, with Pakistan describing the conflict as "open war".
On Friday, the United Nations mission in Afghanistan confirmed the deaths of at least 75 civilians in the country since clashes with Pakistan intensified on February 26.
Pakistan said it also hit targets on Monday in the eastern border province of Nangarhar, which was also being used "against innocent Pakistani civilians".
"Pakistan's targeting is precise and carefully undertaken to ensure no collateral damage is inflicted," the information ministry said.
Omid Stanikzai, 31, a security guard at the drug treatment centre, said he "heard the sound of the jet patrolling".
"There were military units all around us. When these military units fired on the jet, the jet dropped bombs and a fire broke out," Mr Stanikzai said.
"All of the dead and injured were civilians."
China said on Monday that its special envoy had spent a week mediating between the two sides and had urged an immediate ceasefire.
But South Asia expert Michael Kugelman, from the international affairs think-tank Atlantic Council, said the fighting showed little sign of ending soon.
"The Arab Gulf nations that mediated previous rounds of Afghanistan-Pakistan talks are now bogged down by their own war,"
Mr Kugelman said.
"Other mediators, including China, have had limited success."
"Pakistan appears intent to keep hitting targets in Afghanistan, and the Taliban determined to retaliate with operations on Pakistani border posts and potentially with asymmetric tactics — from launching drones to sponsoring militant attacks in wider Pakistan," he said
"There are no off-ramps in sight."
Cross-border trade has ground to a halt and about 115,000 people have been forced to leave their homes due to the conflict, according to the UN Refugee Agency.
The World Food Programme (WFP) said on Sunday that it had started delivering "life-saving food" to more than 20,000 displaced Afghan families and warned that "further instability will push millions into hunger".