Syria's army seized an area north of Aleppo on Sunday and killed insurgents as fierce battles raged over the strategic territory, a group monitoring the war and state media reported.

Syria's second city is at the heart of clashes between pro-government forces and a range of insurgents, including al Qaeda's Syria wing, Islamist brigades and Western-backed rebels.

The United Nations Syria envoy Staffan de Mistura is seeking a local ceasefire in Aleppo to allow badly-needed humanitarian assistance into the divided northern city.

Insurgent-held districts have been flattened by Syrian air force bombardments, including barrel bombs - crude explosive devices packed with shrapnel and nails.

Pro-government forces captured an area east of al-Malah farms outside Aleppoand is now aiming to secure parts in the west and cut off insurgent supply lines into the city, the Britain-based Syrian Observatory for Human Rights said.

It said 34 fighters from Islamist groups including al Qaeda's Nusra Front were killed when Syria's army attacked their positions with backup from local and foreign militias. It added that there were also battles south and east of the city.

Syria's state news agency said the army was tightening its "grip on terrorists in Aleppo after new advances."

It said pro-government forces had captured all of the al-Malah area as well as areas south and west of Handarat town in the countryside and reported that a "huge number" of enemy fighters had been killed.

Western diplomats have voiced concerns about the ceasefire plan, saying it could be used by the government to take full control of the city and force rebels to surrender, as it did through a previous initiative in the central city of Homs, and then direct its forces elsewhere.

The UN's de Mistura has defended the plan, saying that opposition forces backed the idea and has warned the fall of the city could create an additional 400,000 refugees