GENEVA: Syrian government forces and their militia allies committed crimes against humanity, but rebels have also carried out war crimes, although on a lesser scale, UN investigators said Wednesday.
In their latest report, investigators also blamed President Bashar al-Assad's troops and shabiha allies for the massacre in central Syria's Houla in May when 108 civilians, including 49 children, were killed.
A confidential list of individuals and units believed to have perpetrated the atrocities will be submitted to the UN High Commissioner for Human Rights, they said, in the first step towards seeking accountability for the crimes.
"The commission found reasonable grounds to believe that government forces and the shabiha had committed the crimes against humanity of murder and of torture, war crimes and gross violations of international human rights law and international humanitarian law," the report said.
These "violations were committed pursuant to state policy," added investigators, who were not allowed into Syria to carry out their probe but who spoke to nearly 700 people, including former soldiers who fled the country.
"Large-scale operations in different governorates, their similar modus operandi, their complexity and integrated military-security apparatus indicate the involvement at the highest levels of the armed and security forces and the government," they said.
Shabiha militia loyal to the Assad's regime also "acted in concert with government forces" and were responsible for "many of the crimes" detailed in the 102-page report covering mid-February to July 2012.
A particular incident singled out was the Houla massacre, in which "the commission concluded that the government was responsible for the deaths of civilians as a result of shelling the Houla area and, particularly, Taldou village."
Information garnered from 47 interviews showed that there are "reasonable grounds to believe that" the Houla atrocities "were part of a series of attacks directed against civilians, and as such, formed part of the conclusion that crimes against humanity were perpetrated by the government and shabiha."
Rebel fighters were however not spared in the overall probe, which found them guilty of war crimes, including murder, extrajudicial execution and torture.
Nevertheless, "the violations and abuses committed by anti-government armed groups did not reach the gravity, frequency and scale of those committed by government forces and the shabiha," investigators said in their report which is to be presented to the UN Human Rights Council on September 17.
Overall there has been a significant deterioration of human rights in Syria since the commission's last update to the Council in late June, the report said, with "continuous combat, involving more brutal tactics and new military capabilities on both sides".
Investigators also made a call for their findings to be transmitted to the UN Security Council for action to be taken against perpetrators of the atrocities.
In Washington, US State Department spokeswoman Victoria Nuland voiced regret that Syria's government failed to cooperate with UN investigators and said that the report's conclusions were similar to those of Washington.
"The Commission of Inquiry finds the same thing that we have been saying, which is that the preponderance of the violence, the preponderance of the abuses, are on the side of the regime," Nuland told reporters.
But "obviously, there have been problems" on the rebel side as well, she added.
Publication of the UN report came as a bomb attack targeting military headquarters and a firefight near the prime minister's office in Damascus.
The Free Syria Army claimed the bomb attack targeting a military headquarters near a hotel used by UN observers, saying it was a warning to Assad that it could strike anytime at the very heart of the regime.
At least 63 people were killed on Wednesday in Syria, where more than 23,000 people have died in violence since an uprising against the regime erupted in March 2011, said the Syrian Observatory for Human Rights.