NEAR ALEPPO, Syria – Syrian fighters attacked key military targets and overran two police stations in Aleppo, killing 40 officers, a watchdog said, as the pivotal battle for the commercial capital raged Tuesday. Clashes between the rebels and loyalists of President Bashar Al-Assad were also reported in the capital Damascus, the eastern city of Deir Ezzor and Daraa in the south, cradle of the more than 16-month uprising. The Syrian Observatory for Human Rights said Aleppo was Tuesday rocked by the fiercest fighting of a military offensive on rebels in the city, which came after the government had warned of a looming “mother of all battles.” Rebels used rocket-propelled grenades in pre-dawn attacks on a military court, an air force intelligence headquarters and a branch of the ruling Baath Party in Aleppo, said the Observatory's Rami Abdel Rahman. Later, “hundreds of rebels attacked the police stations in Salhin and Bab Al-Nayrab (neighborhoods) and at least 40 policemen were killed during the fighting, which lasted for hours,” Abdel Rahman said. The police chief was among those killed at the Salhin station in the south of the city, while three vehicles were destroyed, he added. The attacks came as the UN observer mission said government forces were using helicopters, tanks and artillery to fight the rebels, while appealing for both sides to protect civilians in the city of 2.7 million people. Through the night, government troops had shelled the neighborhoods of Salaheddin, Marjeh, Firdoss, Al-Mashhad, Sakhur, Al-Shaar and Ansari, before the army and rebels clashed at dawn in Al-Meesr and Al-Adaa. – Agencies