Syria said almost 90 percent of voters approved a new constitution in a referendum which Washington condemned as "absolutely cynical" as more than 100 people were reportedly killed on Monday.
World powers, meanwhile, piled the pressure on the regime to end its deadly crackdown on dissent.
The charter brought in by President Bashar al-Assad after 11 months of anti-regime protests won 89.4 percent of votes cast in Sunday's referendum, with a turnout of 57.4 percent, Interior Minister Mohammed al-Shaar announced.
The results came as the European Union imposed fresh sanctions on Damascus and while Moscow hit back at US criticism for standing by Assad and frustrating international effort to end the regime's clampdown.
EU foreign ministers agreed to freeze assets of Syria's central bank, impose a travel ban on seven Syrians close to Assad, ban cargo flights into the 27-nation bloc and restrict trade with Damascus in gold and precious metals.
French Foreign Minister Alain Juppe said he wanted Syria dragged before an international court of justice, while Qatari Prime Minister Sheikh Hamad bin Jassem Al-Thani called for the arming of Syrian rebels.
Russian Prime Minister Vladimir Putin slammed the West's "cynical" stance on Syria, staunchly defending Moscow's joint veto with China of two UN Security Council draft resolutions condemning Damascus.
He accused the West of "lacking the patience to work out an adjusted and balanced" resolution that also required opposition forces to cease fire and withdraw from flashpoints such as the besieged central city of Homs.
"A refusal to do so was cynical."
Syrian regime forces on Monday kept up their assault, killing at least 30 civilians, while 11 members of the security forces also died in clashes, the Syrian Observatory for Human Rights said.
Eleven civilians were killed in shelling of the rebel-held district of Baba Amr, in the central city of Homs, under bombardment for a 24th straight day, the monitoring group said.
In what it termed a "massacre," the Observatory's head said armed men killed 68 people on Monday in Homs province and called for an independent investigation to find the perpetrators.
"Sixty-eight civilians were killed today in the western countryside of Homs, in a rural area between the villages of Ram al-Enz and Ghajariyeh, and were taken to the state hospital in the city of Homs," said Rami Abdel Rahman.
"The bodies bore signs of gunfire and knife wounds," the head of the Britain-based monitoring group added.
Signup to our newsletter and follow us on Facebook and Twitter!
"They were killed by 'shabiha' (pro-regime gunmen)," according to the reports received by the Observatory, Abdel Rahman said. "But we cannot confirm or deny this information."
Efforts to evacuate foreign journalists from the rebel-held Baba Amr district of Homs failed on Monday, a Western diplomatic source in the Syrian capital said.
"The evacuation of journalists did not take place but three wounded Syrians were able to leave in Syrian Red Crescent ambulances," the source said.
The diplomat, speaking on condition of anonymity, told AFP earlier that talks and preparations were taking place to rescue two wounded Western reporters trapped in Baba Amr.
The ICRC has been negotiating to rescue the wounded Western journalists from Homs -- under assault by regime forces for more than three weeks -- and retrieve the bodies of two others killed there last week.
British photographer Paul Conroy and French reporter Edith Bouvier were wounded in the attack on Wednesday which claimed the lives of American war correspondent Marie Colvin and French photographer Remi Ochlik.
In Washington, State Department spokeswoman Victoria Nuland asked how a democratic process such as Sunday's referendum could take place in the country while Syrian government guns and tanks were still firing.
"We dismiss it as absolutely cynical," Nuland told reporters.
"Even the referendum that they put forward is ridiculous in the sense that it requires that the state approve any of these patriotic opposition groups," Nuland said.
The draft text of the constitution that was overwhelmingly approved by voters ends the legal basis for the five-decade stranglehold on power of Assad's ruling Baath party but still leaves huge powers in his hands.
The Syrian opposition says the changes are cosmetic after nearly a year of repression by Assad's security forces that human rights groups say has left more than 7,600 people dead.
The United Nations also doubts the credibility of the referendum held amid "pervasive violence," a UN spokesman said.
Any vote in Syria must be held "in conditions free of violence and intimidation," UN deputy spokesman Eduardo del Buey told reporters, adding that UN chief Ban Ki-moon had just "noted" the vote.
"While a new constitution and the end of the Baath party monopoly on power could be part of a political solution, a referendum must take place in conditions free of violence and intimidation," del Buey said.
"It is unlikely to be credible in a context of pervasive violence and mass human rights violations," he added.