The Syrian Revolution General Commission said that 71 people were killed in operations staged on Saturday and Sunday in ongoing crackdown in the country.
The commission said 71 people were killed in operations in Damascus, Homs, Hama, Idlib and Aleppo.
UN-Arab League Special Envoy to Syria Kofi Annan presented a peace plan last month. The six-point peace plan includes demands for a ceasefire, the immediate withdrawal of heavy armor from residential areas and access for humanitarian aid.
The plan was presented to Syrian President Bashar al-Assad on March 10 and accepted by him on March 27.
The ceasefire came into effect on April 12, but although the overall level of violence has dropped since then, al-Assad's government has been accused of failing to abide by key terms of the truce plan, including pulling all forces from urban areas and allowing peaceful demonstrations.