U.N. investigators have said there are strong suspicions that pro-regime gunmen are responsible for at least some of the killings during the Houla massacre, which occurred over several hours starting late last Friday. The government denies any role and blames rebel fighters.
Members of the U.N.'s top human rights body overwhelmingly decided Friday to condemn Syria over the killings, with only Russia, China and Cuba voting against the U.S.-backed resolution. Russia and China have twice shielded Assad's regime from the United Nations sanctions over his crackdown on protests.
But Russian President Vladimir Putin insisted Friday that Moscow wants to help Annan achieve "positive results" and prevent an all-out civil war in Syria. He rejected assertions that Moscow is propping up Assad's regime.
"We don't support any of the parties that are creating threats of a civil war," he told reporters in Berlin.
In fresh violence Friday, Syrian security forces opened fire as thousands of protesters poured into the streets to mark the Houla massacre, activists said. Activists said at least five people were killed in shooting in the northern provinces of Aleppo and Idlib and the southern Daraa province.
Gunmen also reportedly killed 11 workers on their way to work Thursday at a state-owned fertilizer factory in the central province of Homs the third mass killing reported in Syria in a week.
Annan stuck by his six-point roadmap during a visit to Beirut on Friday, but said Syrian President Bashar Assad must send "a signal to his people and the international community that he is determined to implement the plan and that he is going to move ahead in search of peace."
"I know we are all impatient, we are all frustrated by the violence, by the killings ... I think perhaps I am more frustrated than most of you because I am in the thick of things," he told reporters at a press conference.
With Syria growing increasingly chaotic in recent months, the U.N.'s top human rights official echoed warnings that the country was veering toward all-out civil war.
Navi Pillay, the U.N. High Commissioner for Human Rights, appealed for continued support for Annan's plan during an emergency meeting of the Geneva-based U.N. Human Rights Council.
"Otherwise, the situation in Syria might descend into a full-fledged conflict and the future of the country, as well as the region as a whole could be in grave danger," Pillay said in a speech read out on her behalf as countries lined up to express their horror about the massacre in a cluster of villages known as Houla.
Syria's ambassador to the U.N. in Geneva, Fayssal al-Hamwi, also condemned the killings but blamed them on "groups of armed terrorists" seeking to ignite sectarian strife.
The government restricts journalists from moving freely, making it nearly impossible to independently verify accounts from either side.
Meanwhile, Syrian protesters came under fire from government troops in the southern province of Daraa, the suburbs of Damascus and Aleppo, the country's largest city, and Idlib, according to the Britain-based Syrian Observatory for Human Rights.
An amateur video said to be taken in the posh Damascus neighborhood of Mazzeh showed scores of people inside a mosque chanting "Death is better than humiliation!" and accusing the Syrian army of being traitors.
The Observatory also said gunmen killed 11 workers at a state-owned fertilizer factory near the town of Qusair in Homs province.
The opposition and the government traded blame for the killings.
An amateur video posted online by activists purports to show the bloodied bodies of the Bouayda victims lying face down at a makeshift hospital in Qusair. The muffled sounds of men crying could be heard in the background as a person tries to resuscitate one of the workers.
On Thursday, 13 bound corpses, many apparently shot execution-style, were found in the eastern province of Deir el-Zour near the Iraqi border. The men were believed to be workers for an oil company. It was unclear who killed them.
The U.N. said in March that more than 9,000 people have been killed in the conflict. Activists have put the toll far higher, saying 13,000 have died. The uprising began in March 2011 with largely peaceful protests calling for reform but morphed into an insurgency as the government launched a brutal crackdown and many in the opposition took up arms.
The Houla massacre was one of the most brutal attacks. Both sides have blamed each other for the killings.
On Thursday, Syria claimed up to 800 rebel fighters carried out the Houla massacre, giving its most comprehensive explanation to date of the bloodshed.
The government's narrative starkly contradicted accounts of witnesses who blamed "shabiha," the shadowy gunmen who operate on behalf of Assad's regime. The U.N. also said it had strong suspicions those pro-regime gunmen were responsible for much of the carnage in Houla.
Even if the shabiha gunmen were responsible for Houla, however, there was no clear evidence that the regime directly ordered the massacre.
In another development, a previously unknown Syrian rebel group said it is holding 11 Lebanese Shiite pilgrims kidnapped on May 22 after crossing into Syria from Turkey on their way to Lebanon. The group calling itself Syrian Rebels in Aleppo said in a statement obtained by Al-Jazeera TV that the hostages are in good health.
The statement included photographs said to be of the hostages and their passports. Al-Jazeera, which aired the photos Thursday night, did not say how it obtained the material. Its authenticity could not be independently verified.
The group claimed five hostages were members of the militant Lebanese Hezbollah group and demanded its leader, Sheik Hassan Nasrallah, apologize for comments he made in a speech last week. The group did not specify which comments they found offensive. Nasrallah, an ally of the Syrian regime, had said the kidnapping would not change his group's stance.
The group said negotiations for the release of the hostages could begin after Nasrallah apologizes.
Nasrallah, speaking through video link to a conference in Beirut Friday, urged the kidnappers to release the hostages.
"If you have a problem with me, there are many ways and means to solve this," he said. "You want to solve it through war, so be it. You want too solve it peacefully, we can ... But leave the innocent people aside."
Associated Press writers Geir Moulson in Berlin and Frank Jordans and John Heilprin in Geneva contributed to this report.
U.N. rights body condemns Syria over Houla massacre
Members of the U.N.'s top human rights body have voted to condemn Syria over the killing of more than 100 civilians last week.
The 47-nation body approved with 41 votes against three a resolution blaming "pro-regime elements" and government troops for the massacre in the Houla region that sparked international outrage.
Russia, China and Cuba voted against the U.S.-backed resolution Friday. Two countries abstained and one member didn't vote.
The resolution also call for an "international, transparent, independent and prompt investigation" into what happened and echoes calls by U.N. rights chief Navi Pillay for the U.N. Security Council to consider referring Syria to the International Criminal Court.