Pakistan launched an airstrike on the Omid rehabilitation hospital in Kabul, killed 400 and injured 250 people.
The strike took place late on Monday evening at the facility that treats people who use drugs.
Taliban officials report that another 250 people suffered injuries in the attack.
The Taliban government condemned the strike and accused Pakistan of targeting civilians.
Taliban spokesmen say the action formed part of a pattern where Pakistan strikes inside Afghanistan without justification.
Pakistan rejects the accusation outright.
Pakistan states that its aircraft struck sites used by terrorists who operate from Afghan soil.
Officials in Islamabad add that the operation formed part of routine efforts against terrorists and that no hospital came under fire.
Tensions run high along the long border between the two countries.
Pakistan accuses the Taliban of harbouring terrorists who cross over and carry out attacks.
The Taliban in turn denies the charges and points to the latest strike as evidence of aggression.
Meanwhile China and the United Nations call for restraint from both sides.
They urge the governments to talk rather than exchange fire.
Access to the hospital area remains restricted so independent checks on the casualty figures prove difficult.
The numbers come directly from Taliban reports and other sources repeat them without full verification.
The incident adds to a series of clashes that flare up whenever security disputes arise between Pakistan and Afghanistan.
