The UN Human Rights Council has called for an investigation into the killing of more than 100 civilians at Houla, and condemned Syria for the massacre.
The forum passed the resolution with a big majority and wants investigators to identify the perpetrators.
Evidence could potentially be used in future criminal prosecutions.
Earlier the UN high commissioner for human rights, Navi Pillay, said the killings in Houla may amount to crimes against humanity.
She urged the international community to "make all efforts to end impunity" and "ensure accountability for perpetrators" of such "atrocities".
Residents of the village of Taldou, in Houla, said militiamen had been sent in early on Saturday after the Syrian army unleashed a barrage of heavy weapons late on Friday in response to a local anti-government protest.
Ms Pillay's office reported on Tuesday that UN investigators had found most of the 108 victims had been shot at close range or stabbed.
"These acts may amount to crimes against humanity and other international crimes, and may be indicative of a pattern of widespread or systematic attacks against civilian populations that have been perpetrated with impunity," Ms Pillay said, in a speech to the council read out by a representative.
Those who ordered attacks were "individually criminally liable", she added, and urged the UN Security council to refer Syria to the International Criminal Court (ICC), a move opposed by Russia and China.
As Syria is not a state party to the ICC the court has no jurisdiction to indict its citizens without a Security Council referral.
Meanwhile opposition activists said there had been another mass killing of civilians by pro-government militiamen.
Thirteen factory workers were forced off a bus and executed on Thursday in al-Buwaida al-Sharqiya, near the western town of Qusair, they said.
Several videos posted online showed bodies with severe wounds to the head and stomach, consistent with being shot at close range.
The activists' account cannot be independently verified, but twice in the past week UN observers on the ground have corroborated similar claims.
Kofi Annan 'frustrated'
The UN Human Rights Council, the world's top human rights body, met on Friday in emergency session - the fourth time it has done so to discuss Syria since the uprising against President Bashar al-Assad began in March 2011.
In the vote, 41 members voted in favour of the US-backed resolution condemning Syria, while Russia, China and Cuba voted against it. Two other countries abstained and one was absent.
The resolution also specifies that there should be an "international, transparent, independent and prompt investigation".
The UN and Arab League envoy to Syria, Kofi Annan, said he was frustrated at the continued violence despite the acceptance by all sides of his six-point peace plan, under which a ceasefire came into force in April.
Foreign arms blamed
On Thursday, a Syrian government investigation into the Houla massacre blamed armed rebel groups seeking to trigger foreign military intervention.
The US permanent representative to the UN, Susan Rice, dismissed the finding as a "blatant lie".
Syria's representative to the Human Rights Council attacked the resolution's sponsors, among them Turkey and Qatar, saying they bore responsibility for some of the deaths, because, he claimed, they had been supplying weapons to rebel groups.
"No rational person could believe what is being said by some of the sponsors of this session... it is truly despicable," Faisal al-Hamwi said.
Russia has blocked Security Council action against Syria's government, and the Russian foreign ministry appears to support Damascus over Houla.
It issued a statement saying: "The tragedy in Houla showed what can be the outcome of financial aid and smuggling of modern weapons to rebels, recruitment of foreign mercenaries and flirting with various sorts of extremists".
Russian President Vladimir Putin said Russia was not supporting any side in the conflict. And he denied that Russia was supplying Syria with arms "which can be used in a civilian conflict".
Earlier this week, Western diplomats and a human rights organisation reported that a Russian ship carrying arms docked at the Syrian port of Tartus.
Speaking in Oslo on Friday the US Secretary of State, Hillary Clinton, said she did not believe that Russia was neutral.
"We know there has been a very consistent arms trade, even during the past year, coming from Russia to Syria. We also believe the continuous supply of arms from Russia has strengthened the Assad regime," she told a news conference.
UK Foreign Secretary William Hague is meeting representatives of the Syrian opposition in Turkey.
Mr Hague told the BBC that the situation was so grave and deteriorating so rapidly that all options were still on the table.