Local sources in Syria and rights groups say Syrian military helicopters have dropped bombs on rebel-held areas in the northern city of Aleppo.
Amateur video posted online purporting to show the bombed area showed people sifting through charred rubble Saturday.
The latest bombing comes as United Nations Secretary-General Ban Ki-moon called the Syrian situation "the most urgent security challenge in the world today."
Ban said he spoke with U.N. mediator Lakhdar Brahimi, along with U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov, to urge them to influence the warring parties to return to peace talks on February 10.
He also called on both sides, and especially the Syrian government, to allow "unfettered access" to people trapped in blockaded areas beyond the reach of aid.
The first round of peace talks between Syria's warring sides ended Friday with little progress, but did lay a foundation for future negotiations expected next month.
There was little advancement on bringing aid to the hardest-hit areas of Syria's civil war, an issue where many thought common ground could be found.
Aid convoys, however, were able to deliver 1,000 food parcels Saturday to the Yarmouk area, on the southern edge of Damascus. Aid agencies also were evacuating people there, in rare coordination between the government and the opposition.
Brahimi said Friday he was "very, very disappointed" the U.N. has not been able to deliver aid to the besieged, rebel-held city of Homs, where many are said to be starving.
Syria's conflict began in March 2011 as peaceful protests against the government, before spiraling into a civil war that the U.N. says has killed more than 100,000 people and forced nearly 9 million from their homes.