GENEVA (Reuters) - The UN Security Council must investigate "mass killings" by security forces in Syria that may warrant prosecution by the International Criminal Court, an eminent jurists' group said on Sunday. More than 330 people have been killed in five weeks of protests after security forces fired into crowds, and activists continue to be rounded up, the International Commission of Jurists (ICJ) said. The ICJ said the killings occurred in a crackdown on protests since March 15 in Deraa, Latakia, Homs and other cities. Its network of lawyers, human rights defenders and activist groups in Syria had provided the names of most victims. "The Syrian security forces, including members of the presidential guard, and pro-regime militia, are believed to be carrying out these attacks," the Geneva-based group of 52 eminent jurists said in a statement issued overnight. The Security Council must protect peaceful demonstrators from unlawful killings and should examine the situation "with a view to establishing accountability for the perpetrators and justice for victims," ICJ Secretary General Wilder Tayler said. "Those ordering and carrying out these attacks, including those firing live rounds into crowds, must be held criminally accountable," he said. The ICJ urged Syrian authorities to halt what it said was the disproportionate use of force on protesters. "There is enough evidence suggesting mass killings now," Said Benarbia, the ICJ's Middle East and North Africa legal adviser, told Reuters. "Arrests are continuing this morning." Secret police raided homes near Damascus overnight, rights campaigners said on Sunday, as popular opposition to authoritarian President Bashar al-Assad mounted. Security forces and gunmen loyal to Assad killed at least 112 people in the last two days when they fired at protesters demanding political freedoms and an end to corruption on Friday, and on mass funerals for victims a day later. "The Security Council must assess the magnitude of human rights violations," Benarbia said. "It must decide whether to have an international fact-finding mission and if there is enough evidence, refer it to the International Criminal Court," he said, referring to the UN war crimes tribunal in The Hague. The toll included about 25 killed on Friday and Saturday during funerals in the southern city of Deraa, he said. Authorities must immediately release the thousands of protesters whom the ICJ said had been arbitrarily detained during the past five weeks by police and state security. Many families did not know where their loved ones were being held. "Scores of them, including children, were subjected to torture and other ill-treatment," it said.