Syrian military aircraft on Tuesday targeted rebel-held districts in the northern city of Aleppo for the third straight day, killing at least 13 people, activists said, according to AP. The airstrikes were the latest in the regime's air campaign aimed at driving the opposition out of Aleppo, Syria's largest urban center and the country's commercial hub. The opposition has controlled parts the city for more than a year. Government war planes bombed Aleppo's rebel-held Shaar district on Tuesday morning, according to the Britain-based Syrian Observatory for Human Rights. The Observatory, which relies on a network of activists on the ground, said at least two children were among those who died in the attack. On Sunday, 76 people, including 28 children, died in air raids and the city was hit by another round of airstrikes on Monday.