At least 29 people, including 19 children, died in a missile strike by regime forces on the northern Syrian city of Aleppo, a watchdog said Saturday, revising an earlier toll.

"At least 29 people, including 19 children and four women, were killed in Aleppo's Bab Nairab neighbourhood in a surface-to-surface missile strike by regime forces" on Friday, the Syrian Observatory for Human Rights said.

The Britain-based watchdog, which relies on a wide network of medics and activists on the ground, had earlier given a toll of 18 dead, including three children.

A militant group said the toll could rise as rescue operations were still underway on Saturday.

The Observatory said the army was aiming at rebel headquarters, including a base of the jihadist Islamic State of Iraq and the Levant (ISIS), in Bab Nairab, in the south of Aleppo.

"But the missile fell dozens of metres (yards) away," the Observatory said.

An earlier report suggested that more than one missile had been fired.

"My whole family was wiped out, my whole family," a boy in tears said near the rubble of his home, in a video posted by the Observatory.

The militant Syrian Revolution General Commission said in a statement that the death toll could rise as rescuers were still trying to pull people from under the rubble.