The UN Human Rights Council has passed a resolution condemning Syria for "gross violations that may amount to crimes against humanity".
It also established the new post of a special human rights investigator on Syria.
Of the 47 members in the Geneva-based Council, 37 countries voted on Friday for a resolution "strongly condemning the continued widespread, systematic and gross violations of human rights and fundamental freedoms by the Syrian authorities".
Six countries abstained, while four countries - Russia, Cuba, Ecuador and China - voted against the resolution.
The text called for the "main bodies" of the UN to consider a UN report, published on Monday, which found that crimes of humanity had been committed and "take appropriate action".
"We've set the stage in a very substantive way for strong action by the UN if other entities choose to take the opportunity," US ambassador Eileen Chamberlain Donahoe told Reuters news agency.
"The evidence we have seen leaves no doubt about the complicity of Syrian authorities and provides a very strong
basis for accountability to go forward in other institutions where that is their mandate."
Asked whether this meant the International Criminal Court, she replied: "Absolutely, including the ICC if the Security Council chooses to refer this matter."
Catherine Ashton, EU foreign policy chief, said in a statement: "The resolution, adopted by an overwhelming majority, takes our action to a higher level... As long as the repression goes on, we shall continue to press for strong UN action to ensure the safety and protection of the Syrian people."
'Pretext for military action'
Faysal Khabbaz Hamoui, Syria's ambassador to the UN in Geneva, denounced the resolution as "politicised" and aimed at "closing the doors".
UN human rights chief Navi Pillay talks to Al Jazeera
Russia also lambasted the council's findings of gross violations by Syria as "unacceptable" and warned against using them as a pretext for military action.
"The positions [adopted] in the document, which include the veiled hint of the possibility of foreign military intervention under the pretext of defending the Syrian people, are unacceptable to the Russian side," the foreign ministry said in a statement.
Navi Pillay, the UN human rights chief, on Thursday said that her office had received reliable information that the death toll in Syria since the start of the nine-month uprising was now "much more" than 4,000.
Speaking to Al Jazeera from Geneva a day later, Pillay said military intervention in the country is "not on the horizon as a solution".
The UN-appointed investigative panel, which drafted Monday's report, found widespread killings and abuse of dissidents since the start of Assad's crackdown on protests in March.
"November was the deadliest month so far with 56 children killed," the head of the panel, citing "reliable sources", said.
"To date, 307 children were killed by state forces," Paulo Pinheiro told the Geneva-based body.
In-depth coverage of escalating violence across Syria
The panel said Syrian security forces committed crimes against humanity, including the killing and torture of children, after orders from the top of Assad's government.
On Friday, activists reported that security forces killed at least 13 people as thousands marched in anti-government protests across the country following Friday Muslim noon prayers.
The largest protests were held in central Homs province and the city of Hama, Rami Abdel Rahman, the head of the UK-based Syrian Observatory for Human Rights, said.
The demonstrations came a day after army defectors attacked a Syrian air force intelligence base in the northwestern province of Idlib, killing eight people, according to the Observatory.
Meanwhile, on the Syrian-Lebanese border, four Lebanese, including an 11-year-old girl, were wounded while fleeing gunfire coming from across the Syrian side, Lebanese security officials said on Friday.
Al Jazeera's Rula Amin, reporting from the border, said gunfire was heard in the area in the morning.
"A lot of gunfire [was] coming from the Syrian side towards the place where I am, Wadi Khaled, along the border with Syria in Lebanon," she said.