Syrian regime forces edged closer to breaking a long-running rebel siege on two government-held Shiite villages in Aleppo province on Tuesday, backed by heavy Russian air strikes.

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, 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 from Nubol and Zahraa.

The capture was also reported by the Syrian Observatory for Human Rights, a Britain-based monitor, which said government forces had also seized part of the nearby village of Ratyan.

The advances came as Russian planes carried out heavy air strikes throughout the area north of Aleppo city, with the Observatory reporting some 320 raids since Monday morning in the region.

The group said at least 18 civilians had been killed in the raids on Tuesday, including five women, three children and two emergency workers.

At least 26 members of regime forces and 60 rebels also have been killed since the fighting began on Monday, when government forces seized two other villages in the area.

Observatory chief Rami Abdel Rahman said the capture of Ratyan and one smaller village could allow regime forces to effectively break the siege on Nubol and Zahraa, a longstanding government goal.

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.

Last year's government offensive saw troops capture several villages in the area, but it stalled after a rebel counterattack and stormy weather.

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.