A makeshift clinic supported by MSF was destroyed in one attack leaving seven people dead and eight missing in Maarat al-Numan.
The medical charity blamed Russia or Syria’s government for the raid in the province of Idlib.
Separate strikes on another hospital in the same town, as well as on two more hospitals and a school in Azaz in the neighbouring Aleppo province, killed at least 12 people.
MSF said in a statement that the hospital in Maaret al-Numan was hit four times in at least two attacks that were minutes apart.
“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 mission chief.
“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 aid group said the hospital had 30 beds, 54 staff members, two operating theatres, an outpatients department and an emergency room. MSF has been supporting the hospital since September and covered all its needs, including providing medical supplies and running costs, it said.
The Britain-based Syrian Observatory for Human Rights said Russian warplanes targeted the makeshift hospital. The opposition group, which tracks both sides of the conflict through sources on the ground, said dozens were wounded in the attack.
Syrian troops have been advancing in the north under the cover of Russian airstrikes in recent weeks. The offensive has been focused on Aleppo province, where troops are trying to cut rebel supply lines to Turkey and surround rebel-held parts of Aleppo city.
On Monday, Syrian state TV reported that pro-government gunmen have entered western parts of the northern town of Tel Rifaat, where they were fighting “fierce battles’ against insurgents. Tel Rifaat is a major stronghold of militants fighting to overthrow president Bashar al-Assad.
Opposition activist Yahya al-Sobeih, speaking by phone from Maaret al-Numan, said “the entire building has collapsed on the ground.
He said five people were killed near the MSF clinic and “all members of the medical team inside are believed to be dead.”
Paramedics and volunteers were working on removing the rubble at the four-storey building, he added.