A Syrian government official said the number of deaths would likely increase because many of the wounded were in critical condition. Speaking to The Associated Press on condition of anonymity in line with government regulations, he said soldiers killed two more would-be suicide bombers at the scene, before they could detonate their explosives.
Aleppo-based activist Mohammad Saeed said the explosions went off minutes apart at one of the city's main squares. He said the blasts appear to have been caused by car bombs and were followed by clashes and heavy gunfire.
"The area is heavily fortified by security and the presence of shabiha," he said, referring to pro-regime gunmen. "It makes you wonder how car bombs could reach there," he added.
The Britain-based Syrian Observatory for Human Rights, which relies on a network of activists on the ground, reported dozens of casualties from the blasts, most of them members of the regime forces.
A statement from the observatory said the explosions followed a clash between guards at the officers' club and gunmen. It said a fourth car bomb went off in the Bab Jnein area near the Chamber of Commerce, causing an unspecified number of casualties there.
During the course of the 18-month-uprising against Assad, suicide and car bombings targeting security agencies and soldiers have become common in Syria, particularly in the capital, Damascus.
But Aleppo has been spared from such bombings and from the mayhem that struck other Syrian cities, particularly in the first year of the revolt. Then, in February, two suicide car bombers hit security compounds in Aleppo's industrial center, killing 28 people.
The uprising against Assad erupted in March 2011 and gradually morphed into a bloody civil war. The conflict has killed more than 30,000 people, activists say, and has devastated entire neighborhoods in Syria's main cities, including Aleppo.