Syria's state-run news agency says rocket and mortar shells struck a government-controlled neighborhood in the northern city of Aleppo, killing 13 civilians and wounding 40.

SANA says the attack by "terrorists" occurred Sunday in the predominantly Kurdish neighborhood of Sheikh Maqsoud.

Insurgents have been shelling the area for days despite a shaky U.S. and Russian-brokered cease-fire.

The Syrian Observatory for Human Rights, a Britain-based opposition group that monitors the conflict, says the attacks were carried out by the al-Qaida branch in Syria known as the Nusra Front.

The Nusra Front and the Islamic State group are excluded from the cease-fire, which took effect Feb. 27.