Dozens of international aid groups have warned that humanitarian conditions in Syria's north west have reached a new "crisis point", as government troops push to retake the rebels' last stronghold.
The violence has effectively shattered a ceasefire negotiated by Russia and Turkey, in place since September. Russia has firmly backed President Bashar al Assad's government in the eight-year civil war, while Turkey has supported rebel factions.
In their appeal, 70 aid groups called for an immediate end to the fighting. They said the violence has displaced an estimated 180,000 people in the last two weeks alone.
The rebel enclave, which stretches between northern Hama and most of Idlib provinces, is home to three million people.
The violence has forced at least 16 humanitarian organisations to suspend their operations in the region, the groups added. The staff were either displaced themselves or the facilities came under attack.
Physicians for Human Rights said it has verified that over the last four weeks Syrian government forces and their Russian allies have carried out nine attacks on hospitals and medical facilities.
The aid groups said at least 15 health facilities and 16 schools were reported to have been significantly damaged or destroyed. At least two health workers were killed.
The groups said at least four clearly identified humanitarian posts were targeted, and condemned the "failure" to observe international law.
In a statement, Amnesty International called on the UN Security Council to pressure Moscow over the "deliberate" targeting of health and education facilities and to end the "onslaught" against civilians.
"Bombing hospitals carrying out their medical functions is a war crime," said Lynn Maalouf, Amnesty International's director of research for the Middle East. She said it was part of a "well-established" pattern by the Syrian government and its allies.
"The international community has so far utterly failed to protect civilians in Syria from the horrors of this conflict," she said.
Staff from four hospitals in Idlib and Hama told Amnesty International they had been targeted despite sharing their co-ordinates with the Syrian and Russian governments.
In fighting on Friday, activists and insurgents said government forces attempted to push into a new village in western Hama but were repelled.