A Syrian colonel on the ground said government forces were "three kilometres (1.9 miles) from Nubol and Zahraa."
He said they planned to "break the siege on them and cut the only remaining rebel supply route between Aleppo city and the north of the province."
Earlier today, Syrian state news agency SANA said government troops backed by pro-regime militants had "restored security and stability to the village of Hardatneen," about six kilometres away from Nubol and Zahraa.
The advances came as Russian planes carried out heavy air strikes throughout the area north of Aleppo city, with the Observatory reporting some 270 raids since Monday morning in the region.
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The group said at least 18 civilians had been killed in the raids today, including five women, three children and two emergency workers.
It also reported at least 20 members of regime forces and 38 rebels had been killed since the fighting began on Monday, when government forces seized two other villages in the area.
The government advance comes almost exactly a year after a similar regime offensive aimed at reaching Nubol and Zahraa and severing rebel supply lines into Aleppo city.
The city was divided between government control in the west and rebel control in the east after fighting there began in mid-2012.
The situation is largely reversed in the surrounding countryside, with rebels controlling much of the area west of the city, and the regime present to the east.
The current offensive is one of several the government has launched since Russian strikes began on September 30.
More than 260,000 people have been killed in Syria since the conflict started with anti-government protests in March 2011.