At least 21 civilians were killed and 100 injured during a Syrian army air raid over a rebel-held area in Aleppo.
The Syrian Observatory for Human Rights (SOHR) Sunday said the air force had dropped crude barrel bombs on the city of al-Bab, which is occupied by Islamic State (IS) militants, Xinhua reported.
The SOHR said the toll is likely to rise as a large number of people were critically injured.
The incident comes in the wake of the UN envoy to Syria, Staffan de Mistura, arriving at the capital Damascus Saturday for a three-day visit to discuss the renewal of political dialogue in Syria.
