The other 13 council members voted in favor of the resolution, which would have said that the council “fully supports” the Arab League plan.

Mohammed Loulichki, the UN ambassador of Morocco, the sole Arab member of the 15-nation council, voiced his “great regret and disappointment” that Moscow and Beijing joined forces to strike down the resolution.

French Ambassador Gerard Araud told the council, “It is a sad day for this council, a sad day for all Syrians, and a sad day for democracy.”

Diplomats said that China had been expected to follow Russia’s lead. Russia’s decision to vote against the resolution came after US and European officials rejected a series of Russian amendments to the draft resolution.

The setback in diplomatic efforts to defuse the revolt peacefully came after world leaders and Syrian opposition activists accused Assad’s forces of killing hundreds of people in a bombardment of the city of Homs, the bloodiest night in 11 months of upheaval in the pivotal Arab country.

Rift at the Security Council

Shortly before the Security Council voted, US President Barack Obama denounced the “unspeakable assault” on Homs, demanded that Assad leave power immediately and called for UN action against Assad’s “relentless brutality”.

“Yesterday the Syrian government murdered hundreds of Syrian citizens, including women and children, in Homs through shelling and other indiscriminate violence, and Syrian forces continue to prevent hundreds of injured civilians from seeking medical help,” Obama said in a statement. “Any government that brutalizes and massacres its people does not deserve to govern.”

He and other Western and Arab leaders put unprecedented pressure on Assad’s veto-wielding ally Russia to allow the Security Council to pass a resolution backing an Arab League call for Assad to transfer powers to a deputy.

But US Secretary of State Hillary Clinton said on Saturday it had not been possible to work constructively with Russia ahead of the vote, even though military intervention in Syria — fiercely opposed by Moscow — had been absolutely ruled out.

“I thought that there might be some ways to bridge, even at this last moment, a few of the concerns that the Russians had. I offered to work in a constructive manner to do so. That has not been possible,” she told reporters at the Munich Security Conference.

Moscow said before the vote that the resolution was not “hopeless”, but its wording needed to be altered to avoid “taking sides in a civil war”. Foreign Minister Sergei Lavrov said it was still possible to reach consensus.

But US Ambassador to the United Nations Susan Rice said amendments that Russia had proposed were “unacceptable”.

After what US officials called “vigorous” talks between Clinton and Lavrov, Moscow announced that its foreign minister would fly to Syria in three days to meet Assad.

France called the Homs assault a “massacre” and a “crime against humanity”. Turkey said hundreds had been killed and the United Nations must act. Tunisia expelled the Syrian ambassador, and the flag above its embassy was brought down.

Deadly assault

Death tolls cited by activists and opposition groups ranged from 237 to 260, making the Homs attack the deadliest so far in Assad’s crackdown on protests and one of the bloodiest episodes in the “Arab Spring” of revolts that have swept the region.

Residents said Syrian forces began shelling the Khalidiya neighborhood at around 8 p.m. (1800 GMT) on Friday using artillery and mortars. They said at least 36 houses were completely destroyed with families inside.

“We were sitting inside our house when we started hearing the shelling. We felt shells were falling on our heads,” said Waleed, a resident of Khalidiya.

“The morning has come and we have discovered more bodies, bodies are on the streets,” he said. “Some are still under the rubble. Our movement is better but there is little we can do without ambulances and other things.”

An activist in the neighborhood contacted by Reuters said residents were using primitive tools to rescue people. They feared many were buried under rubble.

“We are not getting any help, there are no ambulances or anything. We are removing the people with our own hands,” he said, adding there were only two field hospitals treating the wounded. Each one had a capacity to deal with 30 people, but he estimated the total number of wounded at 500.

“We have dug out at least 100 bodies so far, they are placed in the two mosques.”

A third Khalidiya resident, speaking by telephone with wailing and cries of “Allahu akbar” (God is greatest) audible in the background, said at least 40 corpses had been retrieved from streets and damaged buildings.

As news of the violence spread, angry crowds of Syrians stormed their country’s embassies in Cairo, London, Berlin and Kuwait and protested in other cities.

In Cairo, a crowd stormed the Syrian embassy, smashing furniture and setting fire to parts of the building in protest over the Homs bloodshed. The gate of the embassy was broken and furniture was smashed on the second floor of the building.

In London, 150 people hurled stones at the Syrian embassy, smashing windows and shouting slogans. Police said five men were arrested after breaking into the building and another held for assaulting police. Kuwait’s KUNA news agency said Syrians broke into the embassy there at dawn, tore down the flag and injured several security guards. Demonstrators burst into the embassy in Berlin, destroying portraits of Assad and his father.

In the cities of Hama and Idlib, activists said hundreds of people took to the streets in solidarity. They chanted in Idlib: “Homs is bombarded, and you are still sleeping?”