GENEVA (Reuters) - Fewer than 20 of the 108 people confirmed as having been killed in the "appalling massacre" in the Syrian town of Houla died from artillery and tank fire, the United Nations human rights office said on Tuesday. Survivors have told U.N. investigators that most of the other victims died in two bouts of summary executions carried out by pro-government Shabbiya militia in the nearby village of Taldaou, U.N. rights spokesman Rupert Colville said. ...