(BEIRUT) — World leaders called Thursday for an urgent cease-fire in Syria as government forces pounded the opposition-controlled eastern suburbs of the capital in a crushing campaign that has left hundreds of people dead in recent days. The U.N. Security Council heard a briefing from U.N. humanitarian chief Mark Lowcock on what he called “the humanitarian disaster unfolding before our eyes” in the rebel-held suburbs known as eastern Ghouta. Sweden and Kuwait were seeking a vote on a resolution ordering a 30-day cease-fire to allow relief agencies to deliver aid and evacuate the critically sick and wounded from besieged areas to receive medical care. But Russia’s U.N.