SURMAN, Syria - Two days of clashes between government forces and armed groups in Syria's last major opposition bastion have killed nearly 70 on both sides, undermining a monthslong cease-fire agreement, a war monitor said on Sunday.

The battles in the northwestern province of Idlib are "the most violent" there since a Russian-brokered cease-fire agreement went into effect in late August, said Rami Abdul Rahman, head of the Syrian Observatory for Human Rights.

Residents of affected villages fled north to escape the fighting, adding to the hundreds of thousands who have already flooded out of the province's violence-plagued south since fighting escalated earlier this year.

"I don't want to see my children trapped under rubble," said a man surnamed Hafez, one of those driven from his home and who escaped the flashpoint area along with his wife and three children two days earlier.

On Sunday morning, clouds of smoke rose over the Maaret al-Numan region as warplanes pounded extremists and allied rebels in positions they had recently recaptured from regime forces, said an AFP correspondent.

The Britain-based Observatory on Sunday put the death toll from fighting at 69 combatants since battles started the previous day. At least 36 government forces were among those killed, it said.

The Observatory said an attack led by Syria's former al-Qaida affiliate on several government positions had initially sparked the fighting.

Overnight, the Syrian army launched a counter-push to reclaim territory it had lost in the battles, the war monitor said.

Government forces have since regained lost ground but violent clashes are ongoing, the Observatory and an AFP correspondent said.

Airstrikes on Sunday afternoon hit extremist-run areas dozens of kilometers away from the main frontline, signaling a potential escalation, the correspondent said.

Idlib, home to around three million people including many displaced by Syria's eight-year civil war, is controlled by the country's former al-Qaida affiliate.

The Hayat Tahrir al-Sham extremist alliance also controls parts of neighboring Aleppo and Latakia provinces, with battles also currently taking place in the latter, according to the monitor.

The region is one of the last holdouts of opposition to the government, which now controls more than 70 percent of the country, according to the Observatory.

Syrian President Bashar al-Assad has repeatedly vowed to reclaim all of Syria, including Idlib, which he views as a "terrorist" holdout.

In August, government troops began a ground offensive that saw them retake several areas in southern Idlib, allowing them their first foothold in the region in years.

Assad, during a visit to the area in October, his first since the start of the eight-year war, said that defeating jihadists in the province was key to ending the conflict.

Agence France - Presse