At least two schools are said to have been hit during the raids
The number of people killed in airstrikes on five medical centres and two schools in northern Syria is close to 50, the UN has said.
Secretary General Ban Ki-Moon described the attacks as "blatant violations of international laws".
One of the strikes was against a hospital in Muratt al Numan run by Western charity Medecins Sans Frontieres (MSF), which blamed Russian or Syrian government forces and claimed it was deliberately targeted.
In a separate attack, blamed by Turkey on Russia, at least 14 people were killed when missiles hit a hospital and school in Azaz near the Turkish border. Russia denied being involved in the airstrikes.
Mr Ban said the attacks "cast a shadow on commitments" made at a Munich conference last week, which included a pledge to hold a ceasefire within a week and end attacks on civilians.
US State Department spokesman John Kirby said they flew "in the face of the unanimous calls by the ISSG (International Syria Support Group), including in Munich, to avoid attacks on civilians, and casts doubt on Russia's willingness and/or ability to help bring to a stop the continued brutality of the Assad regime against its own people".
EU foreign policy chief Federica Mogherini said the MSF hospital attack was "completely unacceptable", but said nothing about who was responsible.
UNICEF executive director Anthony Lake said six of those killed in the attack on schools in Azaz were children.
Turkey has been shelling Kurdish forces near the town from across the border to prevent the YPG - the Kurdish People's Protection Units - advancing on Azaz, which is just 5km from the Turkish frontier.
Turkey regards some Kurdish groups as terrorists and has been carrying out military operations against Kurdish militants in its south.
Kurdish-led forces had recently gained ground along the border with Turkey at the expense of Syrian rebels who had previously captured the territory from forces loyal to the government of Bashar al Assad.
Turkey said on Monday afternoon Kurdish forces had been expelled from around Azaz as a result of its shelling.
The latest strikes come after Russia said a limited ceasefire due to come into effect at the end of this week did not apply to its airstrikes, which have paved the way for major gains by the Syrian army.
Speaking in the capital Damascus last week, Syrian President Bashar al Assad vowed to retake the entire country.