BEIRUT (Reuters) - Syrian rebels using improvised mortar bombs made of cooking gas canisters killed 311 civilians between July and December this year, a monitoring group said on Friday, condemning the use of the wildly inaccurate weapons. Two-thirds of the deaths, or 203 people, were in the northern city of Aleppo where the so-called "hell cannons" have been fired on government-held districts of Syria's second city. The Britain-based Syrian Observatory for Human Rights, which tracks the violence using sources on both sides, said that 42 children and 25 women were among the dead in Aleppo. ...