BEIRUT (AP) — Syrian government forces backed by Lebanese Hezbollah fighters captured several villages near Aleppo in heavy fighting Tuesday that left more than 100 dead on both sides, bringing them closer to their goal of besieging rebel-held neighborhoods in the country's largest city, activists said.

The troops were able to cut off the highway linking Aleppo with the Turkish border, according to Aleppo-based activist Amer Hassan and the Britain-based Syrian Observatory for Human Rights.

Syria's state news agency said troops seized control of six villages and killed "a large number of terrorists." The government refers to all those fighting to oust President Bashar Assad as terrorists.

The Observatory said at least 65 opposition fighters and 50 soldiers and pro-government gunmen were killed in Tuesday's clashes. The Aleppo Media Center activist group and the Observatory both said rebels had regrouped and managed to retake at least one village they lost earlier in the day.

Aleppo, Syria's former commercial capital, has been divided between government and opposition forces since mid-2012. Government forces have been on the offensive, trying to encircle the rebel-held half of the city for months without significant progress — until early Tuesday, when the latest offensive began.

If government forces succeed in fully besieging opposition-held areas, the move will pose the greatest threat to the rebels' position in the area since anti-Assad fighters stormed parts of the city in 2012.

Also Tuesday, U.N. envoy Staffan de Mistura was to brief the Security Council behind closed doors on his meeting last week with Assad in Damascus, in which they discussed the envoy's proposal to freeze hostilities in Aleppo. This is de Mistura's first council briefing since he outlined the plan in October.

"Regime forces made a major push over the past hours," said Hassan, the activist, speaking via Skype from the northern town of Azaz.

Observatory director Rami Abdurrahman said government forces and Hezbollah had been bringing reinforcements into Aleppo province for days ahead of the offensive.

Abdurrahman said government forces are also advancing toward two nearby Shiite villages that have been under siege for nearly two years.