Clashes between anti-government fighters and regime forces killed 51 combattants on both sides in northwestern Syria Tuesday, a war monitor said.

Russia-backed regime fighters have for weeks been chipping away at the edges of the jihadist-run stronghold of Idlib -- a province that borders Turkey -- after bombarding it for months.

China's Syria envoy said Tuesday that "terrorist organisations" including the Islamic State group are being revived in the war-ravaged country, urging the international community not to ignore the "early warning" signs. 

Xie Xiaoyan, Beijing's pointman for the Syrian conflict, made the comments after meeting in Geneva with the UN Special Envoy for Syria, Geir O. Pedersen.

Jihadists and allied rebels withdrew from a key area of northwestern Syria Tuesday as President Bashar al-Assad's forces pressed an offensive against the jihadist-run Idlib region, a war monitor said.

The town of Khan Sheikhun on the region's southern edge has been a key goal for the government as it lies on the main highway through Idlib province connecting the capital Damascus with second city Aleppo.

Regime air strikes on Saturday killed a woman and six of her children in northwest Syria, a war monitor said, a day after Russian bombardment pummelled a nearby displacement camp.

Syria's state-run media say the country's air defenses have responded to a "hostile target" and destroyed the missile before it reached a central Syrian town.

The SANA news agency said on Friday that the projectile had entered the Syrian airspace overnight from Lebanon's airspace, heading toward the town of Masyaf in Hama province.

Syrian state-run media say government forces have captured a northwestern village and are getting closer to the town of Kfar Zeita, which has been held by insurgents since 2012.

The government-controlled Syrian Central Military Media said on Wednesday that troops captured Arbaeen the night before, following intense clashes with al-Qaida-linked militants.

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.