Activists said Hillok district, unlike other opposition held areas in eastern Aleppo, has rarely been hit by government airstrikes in the past six months, leading many from neighboring, less safe areas to move there.
"It is a very densely populated area," said Abu Faisal. He said some of the shops on the 1.5 kilometer- (1-mile-) long street sold gallons of fuel for electrical generators, which apparently caught fire after the bombing. Makeshift hospitals in the area could barely keep up with the casualties, he added.
It is the latest deadly government strike on the city, Syria's largest. Aleppo has been divided between government forces and rebels for nearly two years, with constant fighting doing little to change the balance on the ground.
President Bashar Assad's forces have been carrying out airstrikes and dropping crude barrel bombs in rebel-held districts in the eastern part of the city, at times hitting schools, mosques and markets. The attacks have increased in the last two weeks, suggesting the government was stepping up its offensive in the city ahead of planned presidential elections June 3.
On Wednesday, a government airstrike that hit a school in Aleppo killed 20 people, including 17 children, activists said. The attack took place as teachers and students were preparing an exhibit of children's drawings depicting Syria at war, activists said.
Last week, government airstrikes struck a crowded vegetable market in the opposition-held town of Atareb in Aleppo province, killing at least 30 people and wounding many others.
The main, Western-backed Syrian opposition group, the Syrian National Coalition, condemned Thursday's attack.
"The international community must take immediate measures to protect civilians from airstrikes and neutralize the regime's aircraft, which are showering Aleppo neighborhoods with barrels of death every day while the entire world watches," it said.
Also on Thursday, activists said clashes between Syrian government forces and opposition fighters killed 14 rebels overnight along a strategic corridor between Damascus and the Lebanese border.
The fighting in Zabadani — a town near Damascus and the last rebel stronghold in the area — is part of the larger battle for control of the mountainous Qalamoun region, stretching from the Syrian capital to the border with Lebanon.
Rebels in the capital's suburbs have been firing mortars into the Damascus, the seat of Assad's government, and militants also have struck back with car bombs.
Syrian state news agency SANA said mortar fire killed a man and wounded two teachers Thursday in central Damascus. Mortar fire in the town of Jaramana just outside the city killed a child and wounded 22 people, the agency said.
Earlier this week, a double car bombing in a pro-government district in the central city of Homs and a mortar strike in Damascus killed at least 54 people. Human Rights Watch said in a statement released Thursday that both of those attacks targeted civilians.
"The deliberate targeting of civilians is a war crime, and if carried out in a widespread or systematic way amounts to crimes against humanity," the group said. It called on the U.N. Security Council, which has been unable to stop the conflict in Syria, to impose an arms embargo on any groups implicated in systematic human rights abuses, including the Syrian government.