Syrian forces have further advanced in the northwestern city of Aleppo, closing in on the positions of the militants.

Backed by Russian aerial cover, Syrian army troops were able to make fresh gains in the northern areas of Aleppo and reached the outskirts of the district of the district of Heluk on Sunday.

Russian warplanes also attacked the militant positions overnight.

If the Syrian forces manage to retake Heluk and two other districts of Bustan al0Basha and Sakhur, which are controlled by the militants, there will be a small militant-held section left remained in the city's southeast.

Aleppo has been divided into two parts since the militants gained ground in 2012. government forces are in control of the west and the militants' positions are in the eastern part of the city.

The Syrian army, with the help of Russian fighter jets, have attempted to free the trapped people of the city. The army began a major offensive on September 22 to end the militants' control over the eastern parts of Aleppo.

Washington has been criticized for not doing enough to rein in militants inside the war-torn country to protect a truce which was brokered by the US and Russia in Syria.

The foreign-backed conflict in Syria started in March 2011 and has claimed the lives of more than 400,000 people, according to a UN report.