SYRIAN Government forces have committed human rights violations, including executions, across the country "on an alarming scale" during military operations in the past three months, United Nations investigators said yesterday.

Their report, presented by investigation head Paulo Pinheiro to the UN Human Rights Council in Geneva, also listed multiple killings and kidnappings by armed opposition groups trying to topple President Bashar al Assad.

"The situation on the ground is dangerously and quickly deteriorating," the 20-page report said. "In the increasingly militarised context, human rights violations are occurring across the country on an alarming scale during military operations against locations believed to be hosting defectors and/or those perceived as affiliated with anti-government armed groups, including the Free Syrian Army," it said.

Syria's ambassador dismissed the accusations and threatened to end co-operation with international agencies.

The investigation's report also said it was unable to determine who carried out a massacre of more than 100 people in Houla in May but that forces loyal to Mr Assad may have carried out many of the killings.

Mr Pinheiro, who made a first visit to Damascus at the weekend for talks with senior Syrian officials, had discussed the Houla investigation with the authorities and believed the team would be able to begin working inside Syria, he told the 47-member forum.

Syria's ambassador, Faysal Khabbaz Hamoui, took the floor in the debate to dismiss the accusations as being based on testimony from people fleeing justice and "tendentious media".

Denouncing the meeting as politicised, he said: "This all induces us to seriously consider ceasing all forms of co-operation with agencies concerned as long as they are powerless to provide a constructive solution to the problems."

Russian diplomat Vassily Nebenzia, whose country is Mr Assad's main defender, said Syrian militants were carrying out daily attacks on state institutions and infrastructure and killing civilians.

Western powers called for Mr Pinheiro's commission to be given "full and unfettered access" to Syria immediately.

The UN team, which conducted nearly 400 interviews, said it had collected photographs, videos, satellite imagery and other documentary evidence during its recent investigative missions in the region. It was updating its list of identified perpetrators for possible use in future criminal prosecutions for war crimes and crimes against humanity.

l Gunmen stormed a pro-government Syrian TV channel headquarters yesterday, bombing buildings and shooting dead three employees, state media said, in one of the boldest attacks yet on a symbol of the authoritarian state.

The dawn attack on Ikhbariya Television's offices, located 15 miles south of the capital, as well as overnight fighting on the outskirts of Damascus showed the 16 months of violence was now rapidly encroaching on the capital.

Ikhbariya resumed broadcasting shortly after the attack, displaying bullet holes in its two-storey concrete building and pools of blood on the floor. One building had been almost completely destroyed.