U.S. Secretary of State Hillary Rodham Clinton is calling for "friends of democratic Syria" to unite and rally against President Bashar Assad's regime.

Speaking Sunday in the Bulgarian capital Sofia, the day after Russia and China blocked a UN Security Council declaration on Syria, Clinton said the international community had a duty to halt ongoing bloodshed and promote a political transition that would see Assad step down.

She said the "friends of Syria" could work with opposition groups to promote those goals.

Such a group could be similar to the Contact Group on Libya, which oversaw international help for opponents of the late deposed Libyan leader Moammar Gadhafi.

"We will work to seek regional and national sanctions against Syria and strenghten the ones we have," said Clinton. "They will be implemented to the fullest to dry up the sources of funding and the arms shipments that are keeping the regime's war machine going."

Embassies attacked

Meanwhile, protesters attacked seven Syrian embassies around the world after the Security Council failed to pass the resolution.

About 40 men ransacked the Syrian embassy in the Australian capital, Canberra late Saturday. Protesters smashed windows and threw plants around the premises, but no injuries were reported.

Earlier, demonstrators stormed five Syrian embassies in Europe and the Middle East. They were able to break windows or force their way in at embassies in London, Athens, Berlin, Cairo and Kuwait.

A few dozen Canadians of Syrian descent protested in front of Syria's embassy in Ottawa, calling on the international community to intervene and end the violence in Syria. The RCMP are investigating after someone splashed red paint on the embassy.

Opponents of the Assad regime are particularly angry over what they have described as the deadliest military offensive since the anti-government uprising began last March. Activists say more than 200 people were killed late Friday and into Saturday in the central Syrian city of Homs.

While 13 countries in the 15-member Security Council voted Saturday to adopt the draft resolution, Russia and China used their veto power to block it.

Syria's largest opposition group, the Syrian National Council, said failure to pass the resolution has given the Syrian regime a "licence to kill" with impunity, leading to expectations the Assad government will now step up its efforts to stifle defiance wherever it finds it.

Canadian Foreign Affairs Minister John Baird said the failure by the council to effectively respond to the crisis in the Middle-Eastern country was "yet another free pass for the illegitimate Assad regime and those backing it."

Regime 'morally bankrupt,' Baird says

"Those attempting to cling to power in Syria are morally bankrupt, and their disregard for human life is surpassed only by their cynicism over doing what is just and right," he said in a statement.

The Free Syrian Army, the armed rebels who have been increasingly activity recently, has also vowed to step up its resistance against the Assad regime, which has denied reports of the weekend assault in Homs, calling them part of a "hysterical campaign" of incitement by armed groups against the government.

The UN said in December that more than 5,400 people have been killed in Syria since March, but it has been unable to update its count for weeks due to recent chaos in the country.

Russia is feeling the international pressure that continues to build. Its foreign minister, Sergei Lavrov, is expected in Damascus for talks with President Bashar al-Assad on Tuesday.

The Russians have said they would like to preside over a dialogue between the regime and the opposition to find a political solution to the crisis.

At a gathering of security officials in Germany on Saturday, Qatar's minister for international co-operation said Arab nations had addressed Russia's fears over the resolution.

"We say there will not be a military intervention, there will not be removal of the regime, and the economic embargo (is) optional to the Arab states," Khaled al-Attiyah said at the Munich Security Conference.

With files from The Associated Press