Amnesty International on Monday (May 11th) said it has documented 18 attacks in north-west Syria carried out by Syrian regime and Russian forces over the past year that amounted to "war crimes".

Russia-backed regime forces have since late April 2019 waged two deadly military campaigns in Idlib province, home to some three million people.

A ceasefire has largely held since early March, but hundreds of thousands remain displaced and highly dependent on aid even as the region braces for a possible outbreak of novel coronavirus (COVID-19).

The rights group said it documented 18 attacks on medical facilities and schools by either the regime or Russia between May 5th, 2019 and February 15th of this year, in and adjoining the opposition stronghold.

"Evidence shows that, in their entirety, the documented attacks by Syrian and Russian government forces entailed a myriad of serious violations of international humanitarian law," it said.

"These violations amount to war crimes."

Amnesty said the incidents included three ground attacks and two barrel bomb attacks by Syrian regime forces, as well as airstrikes by both or either side.

Most occurred in January and February, during the latest onslaught, which since December has killed around 500 civilians and displaced almost a million, it said.

Among the documented attacks were Russian airstrikes near a hospital in Ariha on January 29th that flattened at least two residential buildings and killed 11 civilians, it said.

Amnesty also blamed the Syrian regime for an attack on a school using internationally banned cluster munitions that killed three people in Idlib city on February 25th.

"The latest offensive continued an abhorrent pattern of widespread and systematic attacks aimed at terrorising the civilian population," said Amnesty's regional director Heba Morayef.

"Russia has continued to provide invaluable military support -- including by directly carrying out unlawful airstrikes -- despite evidence that it is facilitating the Syrian military's commission of war crimes and crimes against humanity."

Deadly clashes in Idlib

Meanwhile, clashes in north-west Syria on Sunday killed 48 regime fighters and extremists in the highest such death toll since the start of the two-month-old ceasefire, the Syrian Observatory for Human Rights said.

Before dawn on Sunday, armed groups attacked the positions of pro-regime fighters on the western flank of the region, the Observatory said.

The clashes in the Sahl al-Ghab area killed 35 regime fighters as well as 13 extremists, including from al-Qaeda-affiliated Hurras al-Deen, it said.

"It is the highest death toll for fighters since the truce came into force," said Observatory head Rami Abdel Rahman.

"There had been intermittent clashes and mutual bombardment between both sides before, but this is the most violent attack yet."

Abdel Rahman said clashes were ongoing after dark on Sunday night.