From Ivan Watson

A Scud missile slammed into a crowded slum in Syria's largest city overnight, killing at least 50 people and strewing body parts across the neighborhood, opposition activists said Tuesday.

The missile - one of at least eight fired at the ravaged city of Aleppo by government forces since Friday, according to a U.S. official - slammed into the Jabal Badro neighborhood Monday night, the Local Coordination Committees of Syria reported. The blast knocked down seven buildings, leaving residents struggling to dig the mutilated remains of their neighbors out of the rubble, the group said.

"We documented 21 victims by names, but there are completely mutilated bodies and body parts," Mohammad Al-Khateeb, an activist from the AleppoMediaCenter, told CNN. "Nobody is sure about the final number of victims yet."

Forces loyal to Syrian President Bashar al-Assad started using surface-to-surface missiles against rebel fighters in December, after the rebels began using captured rockets to bring down government aircraft. Most have hit in fields, away from population centers.

Jabal Badro had no rebel presence, "nor any revolutionary activities," Al-Khateeb told CNN. The dead included about 20 children, he said.

"One guy came to the neighborhood, came to look for his family," Al-Khateeb said. "He told us, 'I have 20 family members living in this neighborhood. I can't find any of them.' "

There was no immediate response to the report from government officials. CNN cannot independently verify many claims from Syria, as the government has severely restricted access by international journalists.

But video and photos released by opposition activists showed dozens of men digging through the rubble of what appeared to have been an entire neighborhood consisting of dozens of homes shattered by the blast. The northeastern part of Aleppo, Syria's largest city and commercial hub, came under attack again Tuesday night from warplanes, not surface-to-surface missiles.

Abu Fares, another activist with the AleppoMediaCenter, said a jet strafed the apartment building he was speaking from. Moments later, CNN reporters heard a whoosh and an explosion that led Fares to end the call so that he could run for cover.

The United Nations says nearly 70,000 people have been killed in Syria since al-Assad launched a crackdown on opposition in March 2011. At least 159 people were killed around the country on Tuesday alone, according to the LCCS, a network of opposition activists.

In Washington, the U.S. official told CNN that Syria has been launching Scuds about twice a day from outside Damascus toward Aleppo. The official could not confirm which Aleppo neighborhoods were hit, however.

The Soviet-era Scud became notorious when Iraq used the medium-range missiles against allied forces and Israel during the 1991 Persian Gulf War. None of the recently launched missiles has struck across the border in Turkey, where the United States, the Netherlands and Germany have deployed Patriot missiles to protect civilians.

The U.S. official said Washington is still watching recent indications that Syria has moved some of its chemical weapons stockpiles. The Obama administration believes those movements are consolidating stockpiles for more secure storage away from opposition strongholds, the official said.