At least 72 people have been killed in Syria's northern Aleppo province by barrel bombs dropped from government helicopters, activists say. The UK-based Syrian Observatory for Human Rights says 60 people died in the strike on al-Bab - a town currently held by Islamic State (IS) militants. It says 12 were killed in a rebel-held quarter of the city of Aleppo. Syria's government has repeatedly denied using barrel bombs - large containers filled with explosives. The Syrian Observatory for Human Rights (SOHR), which gathers information through a network of activists in Syria, called it one of the worst massacres perpetrated...