Two hospitals have been hit in new air strikes in northern Syria, medics and witnesses say, causing a number of deaths and injuries.
In Azaz on the Turkish border, at least 10 people reportedly died, including several in one hospital building.
Medecins Sans Frontieres said eight staff members were missing after another attack in Maarat al-Numan.
The strikes come days after Russia and other world powers agreed to a limited cessation of hostilities in Syria.
Almost five years of civil war in Syria have led to the deaths of more than 250,000 people. More than 11 million people have been displaced.
It was unclear who carried out the latest attacks. MSF did not identify who was responsible for the Maarat al-Numan strikes.
However, Turkish Prime Minister Ahmet Davutoglu said a Russian ballistic missile had hit buildings in Azaz, with children among the dead.
One medic, Juma Rahal, told reporters: “We have been moving scores of screaming children from the hospital.”
Russia has been carrying out air strikes since September in support of Syrian President Bashar al-Assad and against what it terms “terrorists”.
Azaz has seen an influx of thousands of people fleeing advances by the Russian-backed Syrian army in Aleppo province.
The Kurdish YPG militia, which has been making advances in the area, has also targeted Azaz.
Turkey shelled the YPG over the weekend and on Monday promised the “harshest reaction” if Kurdish forces tried to take the town.
Turkey views the YPG militia in Syria as allied to the outlawed PKK, which has carried out a decades-long campaign for Kurdish autonomy within Turkey.
Syria said the Turkish shelling was a violation of its sovereignty and has called on the UN Security Council to act.
MSF said four rockets had hit the hospital in Maarat al-Numan, a rebel-held town about 30km (20 miles) south of the city of Idlib, within minutes of each other on Monday morning.
The Syrian Observatory for Human Rights, a UK-based group which relies on a network of sources on the ground, said nine people were killed, including a child. The raid also left dozens of others wounded, it added.
“This appears to be a deliberate attack on a health structure, and we condemn this attack in the strongest possible terms,” said Massimiliano Rebaudengo, MSF’s head of mission in Syria.
“The destruction of the hospital leaves the local population of around 40,000 people without access to medical services in an active zone of conflict.”
The 30-bed hospital, which MSF had been supporting since September 2015, had 54 staff, two operating theatres, an outpatients department an emergency room.
MSF, which operates medical facilities inside Syria and supports directly more than 150 others, said last week that attacks were further depleting Syria’s already exhausted healthcare system and preventing more people from accessing desperately needed medical care.
Since the start of this year alone, 14 health facilities in Syria have been hit, which MSF said confirmed that hospitals and clinics were no longer places where patients could recover in safety.