Syrian state media say gunmen have stormed the headquarters of a pro-government television station, killing seven employees, while United Nations investigators are accusing President Bashar al-Assad's forces of committing rights violations on “an alarming scale.”

Wednesday's pre-dawn attack on the al-Ikbariya satellite channel near Damascus killed three journalists and four security guards. The station is privately-owned but strongly supports Mr. Assad's government.

Information Minister Omran al-Zohbi said the explosives that destroyed the broadcaster's studios had been planted by “armed terrorists” – the same term the government uses for rebels. But anti-government fighters denied carrying out the attack. They say a unit of the elite Syrian Republican Guard assigned to guard the station had defected and attacked other government soldiers.

The mounting violence came as a United Nations panel investigating human rights violations in Syria said the situation is “dangerously and quickly deteriorating” and that fighting has “escalated dramatically” since an April cease-fire deal.

The investigators say they were unable to conclusively determine who was responsible for a May 25 attack on the central town of Houla, which killed 108 people, but it considers that pro-government forces “may have been responsible for many of the deaths.”

The panel's Brazilian chairman, Paulo Pinheiro, said “gross human rights violations” – including summary executions – are regularly committed by both sides. He said his team is particularly concerned about reports of the opposition using children as medical porters and messengers, and exposing them to the risk of death and injury.

Syria's ambassador to the United Nations in Geneva, Faisal Khabbaz Hamoui, dismissed the accusations against the government and warned Damascus would end its cooperation with human rights bodies. He then walked out of the Human Rights Council meeting.

Also Wednesday, the deputy to international envoy Kofi Annan said that the mediator intends to hold an international meeting on Syria in Geneva on Saturday. Russia's ambassador to the United Nations said Tuesday that Foreign Minister Sergei Lavrov would attend.