The Britain-based Syrian Observatory for Human Rights said the air raid hit Aleppo's Sheikh Maqsoud neighborhood, which rebels seized parts of last weekend after days of heavy fighting with regime troops.
That gain had been the latest opposition advance in an urban warzone that expanded last summer, when rebel fighters took control of several neighborhoods. Aleppo is Syria's largest city and a key front in the civil war raging between President Bashar Assad and those trying to overthrow his regime.
The Observatory said the death toll from Saturday's air raid, near a checkpoint of anti-government Kurdish militiamen known as the Popular Committees, is expected to rise as many others were seriously wounded.
An amateur video of the raid showed people loading the bodies of three bloodied children and two men in the back of a pickup truck as women screamed and explosions went off in the distance. Another boy was seeing lying dead in the street near a burning truck.
The video appeared genuine and corresponded to other AP reporting on the events depicted.
"I saw dead people and cattle in the area," said Aleppo-based activist Mohammed Saeed, who added that he counted 11 bodies.
Both sides are eager to control the strategic district, which is predominantly inhabited by minority Kurds. The neighborhood is located on a hill on the northern edge of Aleppo and overlooks much of the city, giving those who control it the ability to pound districts held by the opposing side with mortars and artillery.
The rebels control large swaths of northern Syria, and captured their first provincial capital—the city of Raqqa—last month. They have also been making gains in recent weeks in the south, seizing military bases and towns in the strategically important region between Damascus and the border with Jordan, about 160 kilometers (100 miles) from the capital.
Meanwhile in Damascus, mortar rounds hit the residential district of Kafar Souseh on the city's western outskirts, killing one person and wounding at least 13, the state-run SANA news agency said. The attacks also caused material damage to stores in the district and set several parked vehicles on fire, SANA said.
The Observatory said mortar rounds also struck the Damascus suburb of Jaramana. There were no immediate reports of casualties.
It was not immediately clear who fired the shells, but mortar rounds have fallen with increasingly regularity in the center of the capital, puncturing the aura of normalcy that the regime has tried to cultivate in the city.
The regime has largely kept the rebels at bay so far in Damascus, although opposition fighters control several suburbs of the capital and look increasingly capable of threatening the heart of the city—and Assad's power.
State-run news agency SANA said government troops dealt a major blow to rebels in areas east of the city known as Eastern Ghouta, adding that the armed forces "cleansed" areas near the airport to the south, all the way to the northeastern suburb of Adra. It did not elaborate.
Eastern Ghouta has been one of the tensest areas in Syria over the past year, with daily clashes and shelling between troops and rebels.
The Observatory also reported clashes between government troops and rebels Saturday in the town of Otaybah east of Damascus.
Also Saturday, the newly elected prime minister of the Western-backed opposition umbrella group, Ghassan Hitto, started reviewing candidates for a planned rebel interim government that will consist of 11 ministries and will be based inside Syria, according to a statement by the Syrian National Coalition.
It said Hitto, who has lived in the United States for many years, aims to "attract the qualified talent and competencies required to manage the upcoming phase of the revolution."
The candidates for ministerial and deputy positions must be Syrian citizens older than 35 years of age, the statement said. It added that high-ranking regime officials or "those who have committed crimes against the Syrian people or have unlawfully seized Syrian property or wealth" will be excluded from consideration.
"The nominee must be an advocate or supporter of the Syrian revolution," the statement said.
The Western-backed opposition alliance has been marred by severe divisions in its ranks since its formation late last year in Qatar, and its leaders are mostly seen as disconnected from the myriad rebel forces fighting inside Syria.
Also Saturday, Russia said U.N. demands for unlimited access "to all facilities in Syria and to all persons" who experts believe are necessary to be interrogated over an alleged chemical attack "are beyond the framework of the investigation."
Both the Syrian government and the rebels have demanded an international investigation into an alleged chemical weapons attack on March 19 that killed 31 people in the northern village of Khan al-Assal. Damascus has formally asked Secretary-General Ban Ki-moon to investigate.
Last month, Ban appointed a former U.N. chemical weapons inspector to Iraq, Ake Sellstrom, to head the U.N. fact-finding mission that will investigate allegations of the reported use of chemical weapons in Syria. Sellstrom, a Swede, now works at a research institute that deals with chemical incidents.