UN secretary general Ban Ki-moon says almost 50 civilians have been killed and many more wounded in missile attacks on at least five medical facilities and two schools in northern Syria, as Russian-backed government troops intensified their push toward the rebel stronghold of Aleppo.

UN deputy spokesman Farhan Haq said Monday that victims of the attacks included children.

He quoted the secretary general as calling the attacks "blatant violations of international laws" that "are further degrading an already devastated health care system and preventing access to education in Syria."

Haq quoted Ban as saying the attacks "cast a shadow on commitments" made by nations seeking to end the Syrian conflict at a conference in Munich on Feb. 11, which included a cessation of hostilities within a week and an end to attacks on civilians.

The death toll from the violence has continued to rise throughout the day, with updated counts being reported by aid groups, activists and emergency workers from various sites hit by the missile strikes.

At least 14 people were killed in the town of Azaz near the Turkish border when missiles slammed into a school sheltering families fleeing the offensive and the children's hospital, two residents and a medic said.

Bombs also hit another refugee shelter south of the town and a convoy of trucks, another resident said.

"We have been moving scores of screaming children from the hospital," said medic Juma Rahal. At least two children were killed and scores of people injured, he said.

Activists posted video online purporting to show the damaged hospital. Three crying babies lay in incubators in a ward littered with broken medical equipment. Reuters could not independently verify the video.

Ceasefire agreement in serious jeopardy, more players could enter the fray as battles in Aleppo continue 1:58

'A deliberate attack'

In a separate incident, missiles hit another hospital in the town of Marat Numan in Idlib province, in north western Syria, said the French president of the Doctors Without Borders charity — also known by its French acronym MSF — which was supporting the hospital.

"There were at least seven deaths among the personnel and the patients, and at least eight MSF personnel have disappeared, and we don't know if they are alive," Mego Terzian told Reuters.

"The author of the strike is clearly ... either the government or Russia," he said, adding that it was not the first time MSF facilities in Syria had been attacked.

Doctors Without Borders says a hospital they support in Idlib province was destroyed by Russian airstrikes. There are currently eight staffers unaccounted for believed to be in the rubble. (Getty)

Canada was among the countries condemning the attacks, in a joint statement released late Monday by Minister of Foreign Affairs Stéphane Dion and Minister of International Delevelopment and La Francophonie Marie-Claude Bibeau.

"Humanitarian staff work in extremely dangerous situations and put their lives on the line to help those in need: over 80 humanitarian staff and volunteers have died in Syria since the start of the crisis. We call for an immediate end to attacks on civilians and bombings, and the termination of siege tactics."

MSF's mission chief Massimiliano Rebaudengo said the strikes appear to be "a deliberate attack on a health structure."

"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," he said.

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 approximate locations of the towns where three separate air attacks destroyed hospitals on Monday. (Google/CBC)

France's foreign minister said attacks on hospitals by the Syrian government and its allies were war crimes.

"I strongly condemn the new deliberate strike against a hospital," Jean-Marc Ayrault said in a statement. "The attacks against medical facilities ...constitute war crimes."

White House national security adviser Susan Rice condemned in the "strongest terms" the bombings in Syria and said they ran counter to commitments made by major powers in Munich last week to reduce hostilities.

Operation to recapture Aleppo

The Syrian Observatory for Human Rights, which tracks violence across the country, said one male nurse was killed and five female nurses, a doctor and one male nurse are believed to be under the rubble in the MSF hospital.

Also in Marat Numan, another strike hit the National Hospital on the north edge of town, killing two nurses, the Observatory said.

Residents in both towns blamed Russian strikes, saying the planes deployed were more numerous and the munitions more powerful than the Syrian military typically used.

Five were killed and 30 were wounded in the attack on the charity clinic in Azaz, according to the Syrian Observatory for Human Rights. (Mujahed Abul Joud/Getty)

Rescue workers and rights groups say Russian bombing has killed scores of civilians at market places, hospitals, schools and residential areas in Syria.

But Moscow has said it is targeting "terrorist groups" and dismissed any suggestion it has killed civilians since beginning its air campaign in support of President Bashar al-Assad's forces in September.

Russian bombing raids on rebel fighters are helping the Syrian army to advance toward Aleppo, the country's largest city and commercial centre before the conflict. If the army takes the city, it will by the Syrian government's biggest victory of the war.

Turkey on the brink

For now, the town of Azaz has been the scene of fierce fighting as Kurdish anti-government forces (YPG), also backed by Russia, advance from the west. They have reached the edge of town, only five kilometres away from the main Bab al Salam border crossing into Turkey.

The Syrian army is advancing from the south and is now within 25 kilometres of Turkey's border.

It's not yet clear if the charity clinic in Azaz was hit by an airstrike or by a sea-launched ballistic missile from Russian warships anchored in the port of Latakia. (Mujahed Abul Joud/Getty)

Both the Kurds and the army want to wrest control of that stretch of border with Turkey from the insurgents that currently hold Azaz.

Threatening to significantly escalate the already dire situation, Turkey warned Monday that Kurdish militia fighters would face the "harshest reaction" if they try to enter Azaz in an effort to extend their influence along the frontier.

Turkey shelled YPG positions for a third day.

"We will not allow Azaz to fall," Turkish Prime Minister Ahmet Davutoglu told reporters on his plane on the way to Ukraine, adding YPG fighters would already have taken Azaz and Tal Rifaat further south had it not been for Turkish artillery firing at them over the weekend.

Turkey has sworn it will not allow Russian-backed Kurdish militias to enter Azaz. An escalation of the situation at the Turkey-Syria risks a confrontation between NATO and Russia. (Bulent Kilic/Getty)

The standoff has increased the risk of direct confrontation between Russia and NATO member Turkey.

Turkey is enraged by the expansion of Kurdish influence in northern Syria, fearing it will encourage separatist ambitions among its own Kurds. It considers the YPG a terrorist group.

Davutoglu said Turkey would make the Menagh air base north of the city of Aleppo "unusable" if the YPG, which seized it over the weekend from Syrian insurgents, did not withdraw. He warned the YPG not to move east of the Afrin region or west of the Euphrates River, long a "red line" for Ankara.