LONDON (AFP/Reuters) - UN Secretary General Ban Ki-moon urged the Assad regime Friday to stop its offensive on Syria’s second city Aleppo, amid fears of an all-out onslaught against rebel forces and civilians, adding he was “deeply” concerned about reports of the possible use of chemical weapons by Syria, and demanded the government state it would not use them “under any circumstances”.“I’m seriously concerned by the escalating violence in Aleppo,” Ban said during a visit to London for the Olympic Games. “I urge the Syrian government to halt the offensive.” “The violence from both sides must stop for the sake of suffering civilians in Syria,” he added, following a meeting with British Foreign Secretary William Hague.“I demand .... that the Syrian authorities categorically state that they will not use chemical or other weapons of mass destruction under any circumstances,” he said.