CNN 's Hamdi Alkhshali contributed to this report . NEW : At least 143 people were killed Sunday , a Syrian opposition group says . The death toll is likely to rise as more bodies are recovered from the rubble of buildings destroyed by airstrikes in Damascus and its suburbs on Saturday. Saturday may have been the deadliest day of the conflict . There could be 100,000 deaths in Syria next year , envoy says .
NEW : At least 143 people were killed Sunday , a Syrian opposition group says . The death toll is likely to rise as more bodies are recovered from the rubble of buildings destroyed by airstrikes in Damascus and its suburbs on Saturday. Saturday may have been the deadliest day of the conflict . There could be 100,000 deaths in Syria next year , envoy says .