Syrian regime artillery fire killed six civilians including a child when it hit a hospital in the last major rebel bastion of Idlib on Sunday, a war monitor said.
The attack on the northwestern town of Atareb came despite a Russian-Turkish ceasefire since March 2020 supposed to protect the wider jihadist-held stronghold.
It "hit the courtyard and main entrance of the hospital inside a cave," killing six civilians including a child and a hospital employee, the Syrian Observatory for Human Rights said.
Eleven others were wounded including healthcare staff, said the Britain-based monitoring group's head Rami Abdel Rahman.
Also on Sunday, artillery fire killed one civilian and wounded three others in the regime-held city of Aleppo, outside the rebel bastion, state news agency SANA said.
The Idlib region is home to 2.9 million people, of whom two thirds have been displaced from their homes by conflict, the United Nations says.
The region on the border with Turkey is controlled by Hayat Tahrir al-Sham, which is led by members of Syria's former Al-Qaeda affiliate, but several rebel groups are also present.
The ceasefire brokered by rebel backer Turkey and regime ally Russia last March stemmed a months-long regime military offensive on the bastion that killed hundreds of civilians and displaced more than a million people.
It has since largely held despite repeated violations including Russian air strikes on the region, according to the Observatory.
Senior UN humanitarian official Mark Cutts described Sunday's attack on the cave hospital as "alarming", while the International Rescue Committee also condemned it.
"Health facilities are protected under international law and should be safe havens in times of crisis," said Rehana Zawar, IRC director for northwest Syria.
Medical facilities have been hit multiple times in the Idlib region during the war.
Between 2016 and 2019, the World Health Organization documented up to 337 attacks on healthcare sites in Syria's northwest.
The civil war has killed more than 388,000 people and displaced millions at home and abroad since starting in 2011 with the brutal repression of anti-government protests.
Seventy percent of healthcare workers have fled Syria since the start of the conflict, while after years of bombardment only 58 percent of hospitals remain fully functional, the UN says.