The U.N.'s new envoy to Syria said on Saturday that President Bashar Assad's regime should realize that the need for change was both "urgent" and "necessary" and that it must meet the "legitimate" demands of the Syrian people. Lakhdar Brahimi's comments came as Syrian warplanes and ground forces pounded the country's largest city, Aleppo, with bombs and mortar rounds while soldiers clashed with rebels in the narrow streets of its old quarter, according to activists. The latest violence shows that government troops are still struggling to regain full control of the city from the lightly-armed rebels nearly five weeks after they stormed their way into it in a surprise offensive. Activists said rebels also captured an air defense facility in the east of the country near the border with Iraq. "The Syrian government realizes more than me the extent of the suffering endured by the Syrian people," Brahimi told al-Arabia on his first day as the new U.N. envoy in Syria, replacing Kofi Annan who quit after his six-point plan including an April 12 cease-fire failed to stop the bloodshed.