Syrian regime forces, backed by airstrikes from their Russian allies, advanced against opposition rebels in the divided city of Aleppo on Sunday, a monitoring group and state media reported.
Regime troops and allied paramilitaries made territorial gains in the northern part of Aleppo, the Syrian Observatory for Human Rights said.
"This advance is significant because it enables the regime to tighten the noose on [opposition] fighters in the city and distract their combat efforts," observatory head Rami Abdel Rahman said.
"The Russians have been instrumental in this advance with their intense air raids in support of the regime forces in Aleppo," Abdel-Rahman told dpa.
He cited unspecified "heavy" casualties among rebels.
Syria's state news agency SANA said that government forces recaptured al-Kindi Hospital and strategic hills on the northern outskirts of Aleppo.
"The army units are tracking down remnants of terrorists in the area," the agency quoted an unnamed military source as saying.
Last month, the forces of Syrian President Bashar al-Assad, supported by Russian airstrikes, started a major attack to regain rebel-held areas in Aleppo. The government forces have since been fighting the opposition on several fronts in Aleppo, a major battleground in Syria's civil war.
An estimated 300,000 people have been under siege by government forces since July in opposition-controlled eastern Aleppo, where residents report declining supplies of basic goods, including food, electricity and medicine.
On Sunday, the Syrian army called on rebels in eastern Aleppo to leave the area, offering them a "safe" departure.
"The two commands of the Syrian and Russian armies guarantee for gunmen a safe exit and access to the necessary assistance,” the army said in a statement carried by SANA.
It added that the insurgents' departure is necessary for civilian residents there "to live a normal life."
There was no comment from the opposition.
In September 2015, Russia started an air campaign in Syria in support of al-Assad, saying it had targeted extremist groups there.
After threatening to end diplomatic engagement with Russia on Syria over its failure to halt airstrikes in Aleppo, US Secretary of State John Kerry called his Russian counterpart Sergei Lavrov Saturday evening to discuss the situation in the beleaguered city, the Russian Foreign Ministry said Sunday.