United Nations human rights chief Navi Pillay said that last week's Houla massacre, in which 108 civilians were killed in Syria, including 49 children and 34 women, could be considered crimes against humanity.
Those who order, help or fail to stop attacks on civilians are individually criminally liable for their actions, Pillay said in Geneva.
The council will officially condemn the attack in the strongest terms on Friday.
“The massacre of civilians of the sort seen last weekend could plunge Syria into a catastrophic civil war -- a civil war from which the country would never recover, U.N. Secretary-General Ban Ki-moon warned on Thursday.
“I demand that the government of Syria act on its commitments under the [Kofi] Annan peace plan. A united international community demands that the Syrian government act on its responsibilities to its people.
The Human Rights Council has drafted a new resolution that would open a comprehensive, independent and unfettered special inquiry ... into the events in Houla to publicly identify those responsible for these atrocities and hold them to account, as well as condemn the killings and the presence of government artillery in civilian areas.
Twenty-seven European Union diplomats have also called for a war crimes probe and demand that “those responsible for serious violations of human rights must be held accountable,” according to the Associated Press.
In response to the international outrage over Houla, Damascus launched its own investigation into the killings. On Thursday, the government announced that 800 rebels carried out the slaughter in order to ignite civil strife.
But U.N. observers and the few witnesses who survived say that the massacre was perpetrated by the Shabbiha, Assad's so-called ghost militia, a group of civilian soldiers loyal to Assad's Alawite clan that unofficially work on the side of the government.
They came to us from [the nearby villages of] Fela and Sharklia. They are Alawite pigs. They attacked us and said 'die you pigs' and left, an unidentified woman injured in Houla told Reuters.
Shabbiha gunmen have also been blamed for executing 13 factory workers on Thursday in al-Buwaida al-Sharqiya, near the western town of Qusair. The militiamen allegedly forced the workers off of a bus and shot them at close range, according to the BBC.
U.S. Ambassador to the U.N. Susan Rice called Syria's investigation an another blatant lie, adding that there is no factual evidence ... that would substantiate the regime's version of what happened.
Part of the victims had been killed by artillery shells. Now that points ever so clearly to the responsibility of the government. Only the government has heavy weapons, has tanks, has howitzers, U.N. peacekeeping chief Herve Ladsous stated in New York on Wednesday.
But there are also victims from individual weapons, victims from knife wounds and that of course is less clear but probably points the way to the shabbihas, the local militia, he said.