Russia has said it is working towards halting fighting in the northern Syrian city of Aleppo, which has been under heavy government bombardment for more than a week.

The comments by military officials that they were negotiating an end to the violence with the Syrian government came after the US called on Russia to pressure Syria to end the military onslaught.

"Currently active negotiations are under way to establish a 'regime of silence' in Aleppo province," Lieutenant-General Sergey Kurylenko was quoted as saying by Russian news agencies on Sunday.

On Saturday, Russia said it would not urge President Bashar al-Assad's forces to halt air raids on the city as they were targeting groups not covered by the ceasefire, which took effect in late February.

Aleppo is not part of the temporary, partial ceasefire which is now in place in the Damascus countryside and Latakia.

Ceasefire talks in Geneva have come under threat as the Syrian opposition threatened to leave if the Assad government did not halt the attacks.

A pro-government newspaper said on Thursday the army was preparing an offensive to recapture all of Aleppo and the surrounding province.

John Kerry, US secretary of state, arrived in Geneva late on Sunday to rescue the talks and the Arab League is holding an emergency meeting to discuss the situation.

Al Jazeera's James Bays, reporting from the Swiss city, said the opposition delegates present at the talks were cynical about Russia's role in the peace efforts.

"The opposition will tell you the Russians aren't here because they are interested in the talks but are instead interested in the military option," our diplomatic editor said.

People And Power: Syria - Under Russia's Fist

Earlier on Sunday, an Al Jazeera source in Aleppo said Syrian government forces dropped barrel bombs in the Hritan, Kafr Dael, Bab al-Haded and Kastelo neighbourhoods.

Most of the fighting was concentrated in the countryside in an apparent attempt to cut off rebel-held areas from supply routes on the Turkish border.

Hospitals have also been bombed: four medical facilities were hit on Friday on both sides of the frontline, the International Committee of the Red Cross (ICRC) said.

'Extreme conflict'

A raid on Wednesday hit a hospital supported by Doctors Without Borders (MSF) and the ICRC as well as nearby housing, killing 30 people.

"Aleppo has been experiencing extreme conflict for four years now and 95 percent of the medical staff in the city has quite understandably already fled," Sam Taylor of the MSF told Al Jazeera from Amman, Jordan.

"There are only 70 to 80 doctors in Aleppo. That's a ridiculously small amount of medical staff trying to deal with enormous amount of trauma injuries.

"Hospitals and other civilian infrastructure is not a target in this war. It's appalling that this level of violence still continues in the year 2016."

At least 253 civilians, including 49 children, have died in shelling, rocket fire and air strikes in Aleppo since the surge in fighting, according to the UK-based Syrian Observatory for Human Rights monitoring group.

In remarks in Istanbul in Turkey on Saturday, Anas al-Abdeh, head of the Istanbul-based opposition National Coalition, accused the government of "war crimes and crimes against humanity" in Aleppo.

Human Rights Watch, the US-based monitoring group, also said air strikes on medical facilities in the city "may amount to war crimes".

Qatar asked for the emergency Arab League session to discuss the situation in Aleppo, a day after Saudi Arabia condemned the Syrian government offensive.

Zouhir al-Shimale contributed to this report from Aleppo