Syrian rebels have launched an offensive aimed at breaking the government's siege of eastern Aleppo, where the UN estimates some 300,000 people are trapped with dwindling food and medical supplies. A rebel military command centre that includes the newly formed group Jabhat Fatah al Sham, the former al-Qaeda linked Nusra Front, and Ahrar al Sham said they had taken over army positions in the southwestern government-held parts of the city in the first few hours of launching the battle to break the siege imposed on rebel-held areas. The Syrian army confirmed on state media that rebels had waged an offensive but said its fighters pushed back insurgents from an airforce artillery base and denied...