Evidence has been uncovered in Syria that implicates President Bashar al-Assad and members of his inner circle in war crimes and crimes against humanity, a top UN official said Monday.

The allegations came as Syrian rebels, including jihadists, captured the historic Christian town of Maalula north of Damascus, according to the Syrian Observatory for Human Rights, a Britain-based monitoring group.

A UN probe into rights violations committed during 33 months of brutal conflict "has produced massive evidence ... (of) very serious crimes, war crimes, crimes against humanity," United Nations human rights chief Navi Pillay said in Geneva.

"The evidence indicates responsibility at the highest level of government, including the head of state."

It is the first time evidence by a UN-mandated commission has directly implicated Assad in crimes committed during Syria's civil war, which has killed an estimated 126,000 people, according to new figures released by the Observatory.

The four-member UN investigative team, which has been probing rights violations since shortly after fighting broke out, has accused both the regime and the rebels of war crimes.

For the first time however, they have now cobbled together a long and confidential list of suspected perpetrators.

With no access to Syria, the investigators had to rely on more than 2,000 interviews in neighbouring countries or by phone or Skype.

Pillay told reporters in Geneva the names would remain sealed until they could be provided to a "credible" national or international investigation, and reiterated her call for the case to be handed over to the International Criminal Court in The Hague to ensure accountability.

"The scale of viciousness of the abuses being perpetrated by elements on both sides almost defies belief," she said.

Chemical arms should not be 'distraction'

Pillay warned that efforts to destroy Syria's massive chemical weapons stockpile should not distract from the tens of thousands of killings with conventional weapons.

The Syrian Observatory, which relies on a network of activists, lawyers and doctors on the ground in Syria, said Monday it had documented 125,835 deaths in the conflict up to December 1.

The dead include 44,381 civilians, among them 6,627 children and 4,454 women.

Adding to Syria's misery, more than one million people are now going hungry because fighting and checkpoints have hindered the delivery of aid, the Red Cross said Monday.

Under a US-Russia deal that headed off US military strikes against Assad's regime after a massive chemical attack earlier this year, Syria is to destroy its chemical arsenal by mid-2014.

While inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) have sealed more than 1,000 tonnes of chemical weapons, the UN official charged with their destruction warned Monday the hardest part is yet to come.

Speaking at an annual meeting of OPCW member states in The Hague, Sigrid Kaag said "the removal of Syria's chemical agents for destruction outside of its territory will require tremendous coordination and collective effort."

Despite international consensus on destroying the chemicals outside war-wracked Syria, no country has volunteered to have them destroyed on its soil.

The OPCW on Saturday said the United States has offered to destroy Syria's most dangerous chemical weapons on a vessel at sea through a process of hydrolysis.

Tyres packed with explosives

On the military front, Syrian rebels on Monday captured Maalula after an assault in which a security source said they sent explosive-filled tyres hurtling down on loyalist forces deployed there.

The capture came after three days of fighting around the picturesque town where a centuries-old Christian community still speaks Aramaic, the ancient language spoken by Jesus Christ.

The rebels abducted 12 Syrian and Lebanese Orthodox nuns from their convent after moving into the town, Vatican Radio reported, citing Mario Zenari, the nuncio (ambassador) of the Holy See in Syria.

The Syrian foreign ministry sent letters to UN chief Ban Ki-moon and the Security Council charging that the rebels were ransacking churches in the town, and called on the international community to intervene.
The fighting comes as the regime battles to gain control of a string of nearby towns and villages along the strategic Damascus-Homs highway north of the capital.

Elsewhere in the country, rebel fighters captured a weapons depot in the southern province of Daraa after several days of fighting, the Observatory said.

In a video distributed by the Observatory, a rebel can be seen trampling the severed head of a soldier killed in the fighting.