In a statement published by the official SANA news agency, the Syrian army promised "a safe exit and access to the necessary assistance" for rebels, guaranteed by the commands of both the Syrian and Russian armies, if rebels left the besieged city of Aleppo.

The departure of the rebels was necessary for civilians "to live a normal life," the statement added.

There was no comment from the rebel ranks.

Advances by Assad forces

Sunday's announcement came as government forces, backed by Russia, tightened their control over the former commercial capital.

Syrian regime forces advanced against opposition rebels in Aleppo, state media and the Syrian Observatory for Human Rights reported. The SANA news agency said forces loyal to President Bashar al Assad had recaptured al-Kindi Hospital and strategic hills on the northern outskirts of Aleppo.

"This advance is significant because it enables the regime to tighten the noose on opposition fighters in the city and distract their combat efforts," said Observatory head Rami Abdel Rahman.

"The Russians have been instrumental in this advance with their intense air raids in support of the regime forces in Aleppo," he told news agencies, adding that rebels had incurred "heavy" casualties.

Kerry, Lavrov discuss Aleppo

On Sunday, US Secretary of State John Kerry called his counterpart in Moscow, Sergey Lavrov, to discuss the worsening situation in the besieged city. They "examined the situation in Syria, including the possibility of normalizing the situation around Aleppo," according to the Russian Foreign Ministry.

Nearly 300,000 people have been trapped in Aleppo ever since government forces - backed by Russia -laid siege on the eastern part of the city. Residents have reported a serious decline in supplies of food, electricity and medicine.

According to the United Nations, at least 320 civilians have been killed since the renewed offensive began on September 22.

mg/cmk (AP, Reuters, dpa)