Clashes between pro-government forces and jihadist-led groups that control Syria's northwest killed at least 45 combatants on Tuesday, a war monitor said.

At least 35 combattants including 26 pro-regime forces were killed Saturday in clashes and air strikes that erupted at dawn in northwestern Syria, a war monitor said.

Regime and Russian air strikes and shelling have killed at least 28 people including seven civilians in embattled northwest Syria, a war monitor said Friday, despite a ceasefire announced by Moscow.

Moscow has announced a ceasefire in Syria's northwestern Idlib province after weeks of intensified rocket fire and air strikes by regime and Russian forces.

"At Russia's initiative, with the mediation of Turkey and Russia, a ceasefire agreement was concluded in the Idlib de-escalation zone as of midnight on June 12," the Russian Reconciliation Centre for Syria said in a statement late Wednesday.

New satellite photos show significant damage to Syrian villages and surrounding farmland as a result of a government offensive on the last rebel stronghold in the country.

The images, provided to The Associated Press by the Colorado-based Maxar Satellites on Tuesday, show fires in olive groves and orchards during harvest season around Kfar Nabudah and Habeet, two villages on the edge of Idlib province where fighting has focused. The fires were apparently sparked by intense bombing in the area.

Syrian air defense batteries on Friday intercepted projectiles coming from Israel and downed a number of them, the official news agency SANA reported.

Belgium, Germany and Kuwait on Wednesday requested an urgent meeting of the UN Security Council to discuss the upsurge in fighting in northwest Syria, diplomats said.

After eight months of relative calm, Syria's northwestern province of Idlib is once again a theater for bloody military operations: heavy bombardment, airstrikes and waves of civilian displacement as Syrian government troops, backed by Russia, push their way into the rebel-held enclave in a widening offensive.

The violence of the past week threatens to completely unravel a crumbling cease-fire agreement reached between Turkey and Russia at the Black Sea resort of Sochi in September last year, which averted a potentially devastating assault by the Syrian government to retake the province.

Russia on Saturday released a former student convicted for trying to enter Syria in a high profile 2016 case after she was granted parole this month. 

Attacks by two jihadist groups killed at least 17 Syrian government troops and militiamen in the northern province of Aleppo early on Saturday, a war monitor said.