BEIRUT — Syrian opposition activists say intense airstrikes on rebel-held parts of the northern city of Aleppo and nearby villages and towns have killed at least 45 people.

The Aleppo Media Center, an activist collective, said 45 people were killed Saturday, just hours after a new U.S.-Russian agreement was reached to try and end the violence in Syria. The Britain-based Syrian Observatory for Human Rights said 69 people were killed in Aleppo province, including 13 children and teenagers.

Contrasting casualty figures are common in the aftermath of large attacks in Syria.

The United States and Russia announced a deal Saturday that would establish a nationwide cease-fire starting on Monday, followed a week later by an new military partnership targeting Islamic State and al-Qaida militants as well as the establishment of new limits on the forces of Syrian President Bashar Assad forces.