The Turkey-based Syrian National Coalition said in a statement that it was forming a commission of inquiry to investigate the incident in Khan al-Assal.
Syrian activists say rebels killed 150 government soldiers, some after they surrendered, on Monday and Tuesday in the village outside Aleppo, the country's largest city.
The state media said that 123 civilians and military personnel were killed in a "massacre" and others were still missing.
"Those involved in such crimes will be held accountable," the SNC statement said.
In a separate statement, the SNC urged Egypt to "immediately release" dozens of Syrians it said were arrested last week allegedly for violating residency regulations. It said Egyptian police arrested at least 72 Syrian men and nine boys at checkpoints on main roads in Cairo. Some had valid visas or residence permits, but were arrested "on the pretext of not having residence permits," it said.
The SNC said the arrests came days after regulations concerning Syrians' entrance into Egypt were changed. Since July 8, Syrians have been required to obtain entry visas and security clearance before they are allowed to enter Egypt.
