The UN says there has been a "dramatic escalation" in violence since Syrian forces started an operation to retake Idlib province. Human rights chief Michelle Bachelet regretted "international indifference."
More than 400,000 people have been displaced in northwestern Syria since the start of a government offensive to retake the region in late April, the United Nations said Friday.
David Swanson from the UN's humanitarian coordination office (OCHA) said more than 2,700 people have died during the "dramatic escalation" in violence in Idlib province.
Russia has been helping government forces loyal to President Bashar Assad with airstrikes, despite an international truce.
UN reports persistent pattern against civilians
UN Commissioner for Human Rights Michelle Bachelet criticized "international indifference" at the number of civilians dying in attacks on schools, hospitals and other civilian targets.
"These are civilian objects, and it seems highly unlikely, given the persistent pattern of such attacks, that they are all being hit by accident," she said.
The UK-based Syrian Observatory for Human Rights said it had registered 39 attacks on health facilities and at least 50 attacks on schools. More than 740 civilians have been killed in those strikes, it added.
Intentional attacks are war crimes
"Intentional attacks against civilians are war crimes, and those who have ordered them or carried them out are criminally responsible for their actions," Bachelet said.
Forces loyal to Assad have retaken around two-thirds of Syria's territory.
The country's civil war has claimed the lives of more than 370,000 people and displaced millions since it began in 2011.
amp/jm (AFP, dpa)