John Kerry, the US secretary of state, has called on Syrian government forces and rebel groups to declare a ceasefire, particularly in Aleppo, as intense fighting continues to ravage the city.
"Both sides - the opposition and the regime - have contributed to this chaos," Kerry told reporters in Geneva, speaking alongside United Nations special envoy to Syria Staffan de Mistura.
"We are working over these next hours intensely in order to try and restore this cessation of hostilities."
Referring to the bombing of the al-Quds hospital and other clinics in the eastern, rebel-controlled part of the city, Kerry said: "The regime has clearly indicated a willingness over a period of time now to attack first responders, to attack healthcare workers and rescue workers. It has to stop."
Kerry said that he would speak to Russian Foreign Minister Sergey Lavrov by telephone on Monday afternoon. De Mistura said he would then travel to Moscow on Tuesday to meet Lavrov.
Diplomatic pressure was mounting to extend a ceasefire to Aleppo province after hundreds of people were killed there over 10 days.
"We are preparing the mechanism, but the mechanism needs the political will," de Mistura said, adding that plans were under way for a "much better mechanism for monitoring and controlling a new ceasefire".
Russian officials said on Sunday that they were calling on the Syrian government to include Aleppo in a temporary truce already in place in Latakia and around the capital Damascus.
'Close to collapse'
Government forces and rebels are battling each other for the city, with each side controlling different neighbourhoods.
As of Sunday, more than 250 civilians, including 49 children and 31 women, had been killed in 10 days of renewed fighting between government forces and rebels, according to the UK-based Syrian Observatory for Human Rights.
The group said 145 civilians were killed by air strikes on rebel-controlled neighbourhoods.
It also said that at least 100 civilians "were killed when tens of shells, homemade rockets and explosive cylinders [hit] places controlled by the regime forces in Aleppo".
The Observatory did not identify the planes attacking rebel-controlled areas.
|More than 200 civilians have been killed in the last 10 days, according to activists [Abdalrhman Ismail/Reuters]
Local journalist Zouhir Al Shimale said an air strike on the Helluk neighbourhood on Monday wounded several people, while at least three people were killed in barrel-bomb attacks on Kafr Hamra in the countryside outside Aleppo.
Russia and the Syrian government had previously said the presence of al-Nusra Front, which was not party to a February 27 ceasefire, justified the offensive on Aleppo.
The Syrian army and the Russian defence ministry said on Monday that the truce around Damascus, which began on Saturday, had been extended for another two days.
Talks in Geneva to agree a lasting, wider ceasefire were in jeopardy as the Syrian opposition said it would walk out if the air strikes on Aleppo did not stop.
Al Jazeera's James Bays, reporting from the Swiss city, said both opposition delegates and diplomats were questioning Russia's role in peace efforts.
"Many diplomats will tell you Russia is not properly invested in this political process, that instead it seems they are pursuing or allowing their allies to pursue a military option," he said.
"The process is very close to collapse if they cannot get the cessation of hostilities back in place."
A Syrian pro-government newspaper said on Thursday that the army was preparing an offensive to recapture all of Aleppo and the surrounding province.
The Arab League is weighing an emergency meeting to discuss the situation.
State news agency SANA said on Sunday that six civilians were killed and 40 others injured in rebel rocket attacks on the residential neighbourhoods of al-Midan, al-Sulaimaniyah and al-Sayyid Ali.
Source: Al Jazeera and agencies