The Syrian government has bombed areas around Damascus as part of its push to keep rebel fighters out of the capital, leaving many children among the dozens killed, anti-regime activists said.
One strike by fighter jets hit the suburb of Moadamiyeh, blasting the walls off apartment blocks and scattering rubble in the streets.
Activist videos posted online showed residents searching for survivors and wrapping dead bodies in blankets. One video showed two corpses lying face down, one covered in gray cement dust. Another showed the bodies of six children laid out on a floor.
The Britain-based Syrian Observatory for Human Rights said 13 people were killed in the Moadamiyeh blast, eight children and five women. The group, which relies on contacts in Syria, also reported deadly air strikes in two other suburbs, saying at least 45 people were killed in and around the capital today, including 10 rebel fighters.
The Syrian government offered its own account of the blast in Moadamiyeh, saying "terrorists" fired a shell at the neighbourhood, hitting a residential building and causing an undefined number of casualties.
The destruction in the videos, however, appeared consistent with an air strike, not a shell attack. Rebel fighters said the strike on Moadamiyeh came amid a government offensive to push rebel fighters from there and the adjacent south-western suburb of Daraya.
Rebels moved into the two suburbs weeks ago, but have been bogged down in clashes with government troops since then. Both areas put rebel forces within striking distance of a key military airport in the Mezzeh neighbourhood. The Observatory said the government had blown up homes between the airport and the neighbourhoods to establish a buffer zone.
The UN says that more than 60,000 people have been killed since Syria's crisis began with anti-regime protests. The conflict has since descended into civil war, with rebel brigades across the country fighting president Bashar Assad's forces.
The secretary general of Nato said that the alliance has no plans to intervene, warning that foreign intervention could have "unpredictable regional repercussions". Anders Fogh Rasmussen told a defence conference in Sweden that Syria is more politically, religiously and ethnically complex than Libya, where Nato air strikes in 2011 helped rebels overthrow Muammar Gaddafi. Still, Nato is deploying Patriot missiles along Turkey's southern border with Syria to help the alliance member guard against spillover from the war.
Russian foreign minister Sergey Lavrov on Monday reiterated his criticism of Western calls for Assad to step down. During a visit to Ukraine, Mr Lavrov suggested that Assad's opponents propose their own solution to the conflict. Syria's splintered opposition has never offered a unified view on how to end the conflict or what should follow, other than agreeing on Assad's removal.