Dozens of Syrian military commanders and officials authorised or gave direct orders for widespread killings, torture and illegal arrests during the wave of anti-government protests that began nine months ago, Human Rights Watch has said.
The 88-page report by the New York-based group, entitled By All Means Necessary: Individual and Command Responsibility for Crimes against Humanity in Syria, is based on more than 60 interviews with defectors from the Syrian military and intelligence agencies.
The report identifies 74 commanders and officials behind the alleged abuse.
"Defectors gave us names, ranks and positions of those who gave the orders to shoot and kill, and each and every official named in this report, up to the very highest levels of the Syrian government, should answer for their crimes against the Syrian people," said Anna Neistat, associate director for emergencies at Human Rights Watch.
The report said the abuses constitute crimes against humanity and that the UN Security Council should refer Syria to the International Criminal Court.
Syria claims armed gangs and terrorists are behind the uprising, not protesters seeking more freedoms and reform in one of the most totalitarian regimes in the Middle East.
In a rare interview on December 7, Syrian President Bashar Assad told US television that he never ordered the brutal suppression of the uprising in his country.
Assad, who commands Syria's armed forces, has sealed off the country to most outsiders while clinging to the allegation that the uprising is the work of foreign extremists.
The United Nations and others dismiss that entirely, blaming the regime for widespread killings, rape and torture. Witnesses and activists inside Syria describe brutal repression, with government forces firing on unarmed protesters and conducting terrifying, house-to-house raids in which families are dragged from their homes in the night.
"Try as he may to distance himself from responsibility for his government's relentless brutality, President Assad's claim that he did not actually order the crackdown does not absolve him of criminal responsibility," Ms Neistat said. "As the commander-in-chief of the armed forces, he must have known about the abuses - if not from his subordinates, then from UN reports and the reports Human Rights Watch sent him."