Airstrikes blamed on Russia hit at least two hospitals and a school in northern Syria on Monday, killing and wounding dozens of civilians and further dimming hopes for a temporary truce, as government troops backed by Russian warplanes pressed a major offensive north of Aleppo.
The raids came days after Russia and other world powers agreed to bring about a pause in fighting that would allow for the delivery of humanitarian aid and the revival of peace talks.
The projected truce agreed on Friday in Munich was to begin in a week, but there was no sign that would happen.
On Monday, Syrian state TV reported that pro-government forces have entered 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 Assad.