France's foreign ministry on Friday accused the Syrian regime of violating a fragile ceasefire in the five-year war that has devastated the country.

A French foreign ministry spokesman condemned the aerial bombardment of opposition forces in the Damascus suburbs on Thursday and said it showed that "the regime is pursuing its actions and violating the ceasefire."

The strikes on Thursday, which the Syrian Observatory of Human Rights said were carried out by Syrian aircraft, came despite a month-long "cessation of hostilities" in Syria between Assad regime forces and their opponents, excluding Daesh and al Qaeda's Nusra Front.

The U.S. State Department also said it was appalled by the reported airstrikes.

"We condemn in the strongest terms any such attacks directed at civilians," spokesman John Kirby said.

In an update late on Thursday, the Observatory said 12 children, nine women, a teacher and an emergency response worker were among the dead in Deir al-Asafir.