ALEPPO — The Syrian army said on Monday it had taken full control of dozens of towns in Aleppo’s northwestern countryside and it would press on with its campaign to wipe out militant groups “wherever they are found.”

The advances were made after President Bashar al-Assad’s forces drove insurgents from the M5 highway linking Aleppo to Damascus, reopening the fastest route between Syria’s two biggest cities for the first time in years in a big strategic gain for Assad.

Assad said on Monday his forces’ rapid recent gains presaged the eventual defeat of the nine-year insurgency that sought to oust him from power. But in an appearance televised by state media, he also cautioned that the conflict was not yet over.

“We know this liberation does not mean the end of the war or the crushing of all plots or the end of terror or the surrender of the enemy, but it definitely rubs their noses in the dirt,” Assad said. “This is a prelude to their (opposition forces’) final defeat, sooner or later.”

Backed by heavy Russian air strikes and aided by pro-Iranian militias, government forces have intensified since the start of the year their campaign to recapture the Aleppo countryside and parts of neighboring Idlib province in the far northwest of Syria where anti-Assad insurgents hold their last strongholds. Russian and government air strikes on Monday hit Darat Izza, near the Turkish border about 30 km (20 miles) north of Aleppo city, wounding several civilians and forcing two hospitals to close, according to hospital staff.

Witnesses also reported air strikes in southern areas of Idlib province in what the opposition said was a “scorched earth policy” that has left dozens of towns and villages in ruins. The advances sent hundreds of thousands of Syrian civilians fleeing towards the border with Turkey in the biggest single displacement of the nine-year-old war.

The United Nations said on Monday that over 875,000 Syrians, mostly children and women, have now fled towns and villages targeted by the heavy aerial bombing campaign since Dec. 1. More than 40,000 have been displaced in the last four days alone from western Aleppo province, the scene of heavy fighting, said David Swanson, a U.N. spokesman.

The offensive has also upset the fragile cooperation between Ankara and Moscow, which back opposing factions in the conflict. Turkish forces and Syrian rebels fought government troops in northwest Syria on Thursday and Russian warplanes struck back in a sharp escalation of an intense battle over the last rebel bastions, Russian and Turkish officials said on Thursday.