Evidence collected by UN inspectors investigating Syrian war crimes implicates senior government officials and, most crucially, President Bashar al-Assad, the UN human rights chief has said Al Jazeera reported.
Navi Pillay, the UN high commissioner for human rights, said in Geneva on Monday that Syrian government officials, including Assad, were also responsible for crimes against humanity.
Her blunt remarks about the head of state were at odds with a policy of keeping the identity of alleged perpetrators under wraps pending any judicial process.
The UN investigators, who collect testimony in utmost secrecy and independently from Pillay, have previously said the evidence points to the highest levels of Syria's government, but have not named Assad or any other officials publicly.
The inspectors have compiled secret lists of suspects and handed them to Pillay for safe storage, in the hope that one day suspects will face trial for crimes including torture and mass killings.
"The scale and viciousness of the abuses almost defies belief," Pillay said.
"They point to the fact that the evidence indicates responsibility at the highest level of government, including the head of state."
But Pillay said even she could not unseal the confidential lists, and insisted she was only repeating what the investigators led by Paulo Pinheiro, a Brazilian expert, had said.
When Pillay was asked to clarify her remarks, she said: "Let me say that I have not said that a head of state is a suspect.
"I was quoting the fact-finding mission, which said that based on their facts, responsibility points at the highest level."
World powers should make accountability for crimes committed in the civil war a priority before the Syrian peace talks scheduled for January 22, Pillay said
In another Syria-related development, Sigrid Kaag, head of the OPCW-UN Joint Mission, said although the country's ability to make chemical weapons had been rendered inoperable, the most complex and challenging work still lay ahead.
Inspectors from the UN and the OPCW, or the Organisation for the Prohibition of Chemical Weapons, have inspected all but one of Syria's chemical weapons-producing sites, and the OPCW has said that Syria's entire stockpile of more than 1,000 tonnes of chemical arms has been placed under seal.
"The removal of Syria's chemical agents for destruction outside of its territory will require tremendous co-ordination and collective effort," Kaag told delegates on Monday at a five-day meeting of the 190 member states of the world's chemical watchdog in the Haig.
However, Faisal Mekdad, Syria's deputy foreign minister, cautioned that the efforts to rid his country of chemical weapons could fail if the international community did not contribute money and equipment including armoured cars to the mission.
Move into Maaloula
On the military front, Syrian rebels moved on Monday into the centre of Maaloula, a historic Christian town, after sending explosive-filled tyres hurtling down on security forces deployed there, a security source said.
The Syrian Observatory for Human Rights, a Britain-based monitoring group, confirmed that rebels had seized part of the picturesque town - where a centuries-old Christian community still speaks Aramaic, the ancient language spoken by Jesus Christ - after five days of fighting.
The rebels abducted 12 Syrian and Lebanese Orthodox nuns from their convent after moving into Maaloula, Vatican Radio reported, citing Mario Zenari, the nuncio [ambassador] of the Holy See in Syria.
The renewed clashes in the town come as the Assad regime battles to gain control of a string of nearby towns and villages along the strategic Damascus-Homs highway north of Damascus.
Elsewhere in Syria, rebel fighters captured a weapons depot in the southern province of Deraa after several days of fighting, the Syrian Observatory said.
In video distributed by the group, a rebel can be seen trampling the severed head of a soldier killed in the fighting.