Regime forces advance into Aleppo under intense airstrike cover

Syrian pro-government forces advanced into the Aleppo battleground amid intense airstrikes on Friday, ahead of fresh diplomatic efforts to end the country's intractable conflict.

Russian and Syrian warplanes pounded opposition-controlled eastern districts, London based Syrian Observatory for Human Rights said, adding the air raids provided cover for forces to advance southwards with the goal of "opening a route to the airport," east of the city.

An estimated 250,000 residents that are currently under siege in Aleppo are unable to receive medical support due to the intensified bombardment in east Aleppo.

"This recent escalation has been huge and we've had a lot of work," said Ibrahim Abu al-Leith, a spokesman for the White Helmets rescue force in Aleppo.

Rescuers were still working to dislodge people from under the rubble in the Tariq al-Bab eastern district, he said.

Meanwhile, the United States and Russia, both of which support opposing sides involved in the five-year war, are expected to meet in Switzerland on Saturday to try to resurrect the peace process after previous failed attempts.

UN Syria envoy Staffan de Mistura will attend, along with the chief diplomats from Turkey, Saudi Arabia and Qatar - all backers of Syrian opposition forces. 

Then in London on Sunday, Kerry will likely meet up with his counterparts from Britain, France and Germany.

Lavrov played down hopes of a breakthrough in Lausanne, telling reporters on Friday he had no "special expectations" for progress. 

Moscow has faced rising international criticism over its backing for President Bashar al-Assad's onslaught in divided Aleppo, including Western accusations of possible war crimes.

Violence has continued unabated in Syria's former commercial hub, which has now been ravaged by Russian and regime airstrikes in support of a major government offensive against rebels.

On Thursday, Moscow offered to "ensure the safe withdrawal" of rebel groups and civilians from eastern Aleppo. There was no immediate response from the rebels.

In an interview with Russian TV aired on Thursday Assad said that Aleppo required “cleaning” in order to “push the terrorists to Turkey to go back to where they come from, or to kill them" claiming that victory in the city would act as a “springboard” enabling the regime to retake all of Syria.

Near Damascus, more than 1,200 people including rebel fighters and their families were bussed out of the towns of Qudsaya and al-Haamah on Thursday under a local deal with the government.