The regime forces and its allies made further advances on Tuesday in a major offensive that could cut insurgents' supply lines between the northwestern city of Aleppo and the Turkish border, the Syrian Observatory for Human Rights said.

The advances, backed by allied militia and heavy Russian air support and which Syrian state media also reported, appear aimed at breaking through rebel-held territory north of Aleppo to reach the Shiite villages of Nubul and al-Zahraa, which remained loyal to Damascus and surrounded by opposition groups.

It is the first major offensive north of Aleppo since Russia began its air campaign in support of Bashar al-Assad on Sept. 30. The city is currently split into areas held by the regime and the opposition.

Damascus and its allies have pressed ahead with a number of offensives in western Syria even as the United Nations tries to advance peace talks in Geneva, recently seizing important towns in the northwest and southwest.

On Monday they seized the strategic village of Hardatnin some 10 kilometers (six miles) northwest of Aleppo, the Observatory said.

The army and allied combatants gained ground in coastal areas last month and have also launched a large-scale assault in southern Syria against insurgents.