The UN General Assembly has backed resolution calling for an end to the violence in Syria, and for President Bashar al-Assad to leave power.
137 countries voted in favour of the motion, 12 voted against and 17 nations abstained. Syria's ambassador Bashar Jaafari warned a vote of support would support opposition "extremists" and "would only lead to a tightening of the crisis, and more violence in the region as a whole".
Foreign Secretary William Hague said the international community had given an "unambiguous" message to the Syrian regime.
"The violence must stop immediately. President Assad and the Syrian regime must heed the call of the international community and allow a peaceful political transition to resolve the crisis. President Assad and those around him should be under no doubt that we will continue to support the Syrian people in their aspiration for a peaceful political transition in Syria.”
The Arab league backed resolution is non-binding, but comes as UN head Ban Ki-Moon condemned "crimes against humanity" in Syria in a press conference.
“On Syria, I continue to be gravely concerned at the level of violence and mounting loss of life," he said. “We see neighborhoods shelled indiscriminately. Hospitals used as torture centers. Children as young as 10 years old jailed and abused. We see almost certain crimes against humanity.”
Russia and China vetoed a similar resolution put before the UN Security Council two weeks ago.
Activists say the city has been under near-constant attack by government forces for almost two weeks.
On Wednesday an explosion at a nearby oil line resulted in a huge cloud of fire and smoke which blanketed the city.
New pictures released of the explosion showed fireballs rising into the air as a man identified by the AP as a citizen journalist and activist stands close by.
Also on Thursday China said it was sending an envoy to the country in an attempt to negotiate a peaceful solution.
Deputy Foreign Minister Zhai Jun will visit Damascus on Friday, China said.
A similar effort by the Russian foreign minister Sergei Lavrov in January ended in little success, officials in the EU, UK and United States have argued.
China and Russia both vetoed a January resolution which called on Syrian president Bashar al-Assad to stand down and cease the violence against civilians.
According to activists almost 7,000 people have been killed in Syria since March.