Syria's main opposition groups rejected on Sunday a new international plan that calls for a transitional government because the compromise agreement did not bar President Bashar Assad from participating.

Their reaction held out little hope for an end to more than 15 months of carnage on a day when the main opposition group said 800 people were killed in violence in the past week alone.

Opposition activists groups say more than 14,000 people have been killed since the uprising against President Bashar Assad's authoritarian rule began in March 2011, or on average about 900 a month. That would make last week's toll alone almost as high as the monthly average as government forces furiously pounded rebellious towns and cities with helicopters, tanks and artillery in an offensive aimed at recovering rebel-held territories.

World powers at a conference in Geneva on Saturday accepted a U.N.-brokered plan calling for creation of a transitional national unity government with full executive powers in Syria.