Afghan Interior Ministry spokesman Qari Saeed Khosty said two explosions occurred at the Sardar Mohammad Daud Khan clinic, followed by gunfire.
The blasts took place at the entrance of the 400-bed hospital located in central Kabul at around 13:00 (local time), he added.
According to witnesses, the attack was carried out with a car bomb, and so far 19 people were killed at the site, not far from the Ministry of Public Health.
There was no immediate attribution of responsibility, but the official Bakhtar news agency quoted witnesses who said that Islamic State of Iraq and Syria (ISIS) fighters entered the health facility. ISIS, which has carried out a series of attacks against mosques and other targets since the Taliban takeover of Kabul in August, staged another action against this hospital in 2017, which left 30 dead.