The United Nations has called on the international community to take action to protect the civilian population in Syria from "ruthless repression" as the country slides into civil war.
More than 4,000 people have been killed, including 307 children, in the military crackdown since March.
Some 14,000 people are believed to be held in detention, an emergency session of the UN Human Rights Council has been told.
"The Syrian authorities' continual ruthless repression, if not stopped now, can drive the country into a full-fledged civil war.
''In light of the manifest failure of the Syrian authorities to protect their citizens, the international community needs to take urgent and effective measures to protect the Syrian people," said United Nations High Commissioner for Human Rights Navi Pillay.
"All acts of murder, torture and other forms of violence must be immediately stopped," Ms Pillay added.
She voiced concern at reports of increased armed attacks by the opposition forces, including the so-called Free Syrian Army, against the Syrian military and security apparatus.
Syrian army deserters killed eight people in an attack on an intelligence building in the north of the country, an opposition group said today.
Ms Pillay, a former UN war crimes judge, noted that she had already called in August for the Security Council to refer Syria to the prosecutor of the International Criminal Court for crimes against humanity.
"The need for international accountability has even greater urgency today," she said.
Crimes against humanity
The 47-member Geneva forum was holding an emergency session on Syria, its third since April, called by the European Union with backing from the United States and Arab countries, including Saudi Arabia.
It followed a report by an independent commission of inquiry, which interviewed 223 victims, witnesses and defectors, that found security and military forces committed crimes against humanity including executions, rape and torture.
"In the light of its findings, the commission is gravely concerned that crimes against humanity have occurred in Syria," Paulo Pinheiro, who led the commission of inquiry, told the talks today.
"The extreme suffering of the population inside and outside Syria must be addressed as a matter of urgency. Victims expect nothing less from the United Nations and its member states," said Mr Pinheiro, a Brazilian expert who headed the three-member panel.
Syria's ambassador to the UN in Geneva, Faysal Khabbaz Hamoui, led his country's delegation to the one-day talks and delivered an angry speech.
"The Syrian problem is one that can be resolved only by Syrians. It is only a domestic, national solution that is possible," he said, referring to democratic reforms promised early next year.
"The solution cannot come from the corridors of the international community," he said. "It is only resolutions trying to put more oil on the fire."
A revised EU draft resolution - which emerged after intense negotiations with China, Cuba and Russia - condemns "continued, widespread, systematic and gross violations of human rights and fundamental freedoms".
But it stopped short of calling for action by the UN Security Council, which has the powers to refer a country to the ICC.