Activists: More than 50 killed in Syria DAMASCUS, Syria, July 14 (UPI) -- More than 50 civilians were killed across Syria by government attacks Saturday, activists said. The Syrian Network for Human Rights and the Damascus Center for Human Rights Studies released a list of 52 people, most identified by name and with ages, and how and where they died. Most were described as killed by shrapnel or indiscriminate shelling in populated areas, and many were children. The United Nations sent a mission to the town of Tremseh, where activists said more than 200 people were massacred Thursday, The Guardian reported. The British newspaper said journalists saw a three-car U.N. convoy heading out of Damascus, and officials confirmed to Spanish news agency EFE its destination was Tremseh. Its observers had confirmed Syrian military planes and helicopters "continued to attack populated urban areas on a large scale," U.N. officials said, logging more than 100 explosions. The Syrian Observatory for Human Rights said a car bombing targeted a state security building in Muhrada Saturday and "a number of state security personnel were killed and wounded." Khirbet Ghazaleh in the Daraa province was surrounded by Syrian army tanks and came under heavy shelling and machine-gun fire, the Local Coordination Committees of Syria said. Syrian state-run TV reported at least three civilians and a security officer were killed by a suicide bomber in a truck in Muhrada. In Tremseh, U.N. observers confirmed government forces had used tanks, artillery and helicopters during Thursday's attack, violating a commitment Syria gave to Kofi Annan, the U.N.-Arab League special envoy, the BBC reported. Annan said he was "shocked and appalled" by the killings, while U.N. Secretary-General Ban Ki-moon said the attack caused "serious doubt" about Syrian President Bashar Assad's commitment to the peace plan. The state-run Syrian Arab News Agency blamed "armed terrorist groups" for the Tremseh violence and said residents called security forces after terrorist groups raided the area, CNN reported. U.S. Secretary of State Hillary Clinton said in a statement Friday she was "deeply saddened and outraged to learn of reports of yet another massacre committed by the Syrian regime that has claimed the lives of over 200 men, women and children in the village of Tremseh." "Credible reports indicate that this unconscionable act was carried out by artillery, tanks, and helicopters -- indisputable evidence that the regime deliberately murdered innocent civilians," Clinton said. Syria cannot be peaceful, stable, or democratic until Assad goes and a political transition begins. We call for an immediate ceasefire in and around Hama to allow the U.N. observer mission to enter Tremseh. Those who committed these atrocities will be identified and held accountable.