British Foreign Secretary William Hague said a suicide bombing that killed two top Syrian security officials on Wednesday showed the need for a UN resolution to end the crisis.
The UN Security Council will later Wednesday vote on a Western resolution renewing the UN mission in Syria that calls for sanctions if the regime does not pull back heavy weapons, but Russia has already rejected it.
"We are aware of reports that the Syrian defence and deputy defence ministers have been killed and a number of others injured by an apparent suicide bombing in Damascus," Hague said in a statement.
"This incident, which we condemn, confirms the urgent need for a Chapter VII resolution of the UN Security Council on Syria."
Chapter VII of the UN charter deals with taking action against threats to peace and acts of aggression.
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Syrian state media said the suicide attack in Damascus killed defence minister General Daoud Rajha and President Bashar al-Assad's brother-in-law Assef Shawkat.
Hague added: "The situation in Syria is clearly deteriorating.
"All the members of the UN Security Council have a responsibility to put their weight behind the enforcement of joint special envoy Kofi Annan's plan to end the violence.
"We call on all parties to refrain from violence, and for the Security Council to shoulder its responsibilities."
Russia and China -- both permanent members of the Security Council along with Britain, France and the United States -- have blocked two previous UN resolutions against Syria.
Russian Foreign Minister Sergei Lavrov on Wednesday rejected the latest resolution, saying it would mean taking sides with a revolutionary movement.