Saturday's attack on the rebel-held northern town killed at least 21 people, mostly in shelling on the hospital, according to the Britain-based Syrian Observatory for Human Rights war monitor.
"We utterly condemn this deadly attack on Al-Shifaa Hospital, one of the largest medical facilities in northern Syria," said IRC's Syria director Wolfgang Gressmann.
"This is the 11th attack on health care that has been recorded so far this year, and brings the total number of verified attacks on health care since January 2019 to 124."
Of the 21 killed, 17 were civilians, including at least 4 hospital staff members, the Observatory said, adding that 23 people were also wounded.
The IRC said the attack completely destroyed the emergency room and the labour and delivery room.
"The hospital is now out of service," the statement said.
"It is vital that these attacks stop."
According to the Observatory, Saturday's artillery fire originated from northern Aleppo province where militias backing Iran and the Syrian regime are deployed near a region run by Kurdish forces.
No one has claimed responsibility for the attack.
The Kurdish-led Syrian Democratic Forces (SDF) issued a statement denying any involvement in the shelling.
The Afrin region, like all areas held by pro-Turkish rebels, regularly witnesses targeted killings, bombings and shootings.
The conflict in Syria has killed nearly 500,000 people since it started in 2011 with the brutal repression of peaceful demonstrations.
