The rights group said it was investigating the scene in the town of Azaz were at least two bombs were dropped by Syrian fighter jets. The attack destroyed a residential block, the group said.
"This horrific attack killed and wounded scores of civilians and destroyed a whole residential block," Anna Neistat, acting emergencies director at Human Rights Watch, said in a statement. "Yet again, Syrian government forces attacked with callous disregard for civilian life."
A report from a U.N. commission on the Syrian crisis found evidence that both parties to the conflict in Syria committed war crimes, though those carried out by pro-government forces were more severe.
The United Nations has been unable to overcome Russian and Chinese objections to a resolution censuring Syria for the bloodshed. The Security Council this week voted against extending a mandate for the observer mission to Syria.
The BBC reported Friday that veteran Austrian diplomat Lakhdar Brahimi will serve as a peace envoy to Syria, replacing former U.N. Secretary-General Kofi Annan.
The British broadcaster adds that unverified video surfaced recently that suggests government forces in Damascus killed at least 60 people, many whose bodies were discovered with their hands tied behind their backs.