Humanitarian teams have begun to evacuate sick and injured women and children from a besieged area of the Syrian city of Homs.
The Red Cross said seven people had been taken to hospital from the Baba Amr district but that it was not clear if two wounded foreign reporters who are stranded in the city were among those moved.
Activists said that Syrian government artillery fire killed at least five people in the district today as the bombardment of opposition-held neighbourhoods entered its third week.
US secretary of state Hillary Clinton tonight described Russia and China’s opposition to UN Security Council action on the Syrian situation as “despicable”.
Mrs Clinton said she was willing to go back to the UN as often as needed in order to end the crackdown by Syrian president Bashar al-Assad on the country’s opposition but added that “we need to change the attitude of the Russian and Chinese governments” in order to make it happen.
She was speaking at the international “Friends of Syria” conference in Tunisia, which is aimed at persuading Syrian president Dr Assad and his allies to accept demands for a democratic transition.
Foreign ministers from more than 50 countries are in the Tunisian capital for the meeting, against the backdrop of a surge in government attacks on the city of Homs and mounting world outrage over violence that has killed thousands of people during the uprising.
The European Union earlier said it would freeze the assets of Syria's central bank from Monday as part of a package of tighter sanctions aimed at stopping a Dr Assad’s crackdown.
"Starting from Monday, we will take new strong measures, notably a freezing of the assets of the Syrian central bank," French foreign minister Alain Juppe told the meeting.
With little sign of any international resolve to intervene to end the violence, Syria's opposition appeared to be taking matters into its own hands, saying it was supplying weapons to rebels inside Syria while Western and other states turned a blind eye.
Delegates said that with efforts to end the violence through the United Nations blocked by Russia and China, the aim of the meeting was to challenge Dr Assad to let in aid and to lay the groundwork for an eventual handover of power in Syria.
"It is very important that the first contact group is taking place today because it sends a message to the Syrian people that we support them in their struggle for freedom and that the international community is clearly committed against the repression and violence of Assad's regime," German foreign minister Guido Westerwelle said in Tunis.
Mrs Clinton said the Assad administration will have even more blood on its hands if it does not agree to an international demand to allow in urgent humanitarian relief.
"If the Assad regime refuses to allow this life-saving aid to reach civilians, it will have even more blood on its hands," she said in Tunis. "So too will those nations that continue to protect and arm the regime. We call on those states that are supplying weapons to kill civilians to halt immediately.”
Highlighting the limits of diplomacy to end the violence so far, a source with the Syrian National Council, the main opposition grouping, said arms were already being ferried to rebels fighting Dr Assad's forces inside Syria.
"We are bringing in defensive and offensive weapons... It is coming from everywhere, including Western countries and it is not difficult to get anything through the borders," the source said in Tunis, speaking on condition of anonymity. "There is not a decision by any country to arm the rebels but countries are allowing Syrians to buy weapons and send them into the country."
The “Friends of Syria” is unlikely to publicly endorse the supply of arms because their public position is that they want a negotiated solution to the violence.
Equally, there was no sign they would try to stop the supplies, seen in many capitals as an unavoidable result of the United Nations' failure to take firm action after Russia and China blocked resolutions on Syria.
A crowd of several hundred Assad supporters tried to force their way into the venue of the meeting, a seaside hotel in a suburb of Tunis, minutes before the session was scheduled to begin. They were held back by Tunisian security forces.
The UN estimated in January that 5,400 people were killed in the conflict last year. Hundreds more have died since. Syrian activists say the death toll is more than 7,300. Overall figures cannot be independently confirmed because Syria has prevented most media from operating inside the country.
In a sign the international community is seeking ways around the Security Council deadlock, UN secretary general Ban Ki-Moon said he would dispatch former UN chief Kofi Annan to Syria as a joint UN-Arab League envoy.
A draft of the declaration to be issued at the meeting called on Syria to "immediately cease all violence" to allow the United Nations access to Homs, and to let agencies deliver aid to civilians affected by the violence.
The draft communique did not mention any foreign military intervention along the lines of the Nato bombing campaign that helped force out Libya's Muammar Gadafy. Instead, it called for further diplomatic pressure on Dr Assad to step down and endorsed an Arab League plan that sees him handing power to a deputy as a prelude to elections.
The group will also commit to enforce sanctions aimed at pressuring Syria authorities to halt violence, according to the draft declaration. These include travel bans, asset freezes, a halt to purchases of Syrian oil, ceasing infrastructure investment and financial services relating to Syria, reducing diplomatic ties and preventing arms shipments to the Syrian government.
Syrian opposition figures said they expected support to be financial, technical and logistical, allowing them to buy satellite phones and equipment to improve coordination on the ground.
In a sign of continued diplomatic pressure on Dr Assad, Turkey said it would host the next "Friends of Syria" meeting.