New violence has erupted in the Syrian town where the uprising against President Bashar al-Assad began 15 months ago. The Syrian Observatory for Human Rights said on Saturday that overnight shelling of Deraa killed 18 people, including 12 women and children. Renewed shelling is also reported in the city of Homs, where the rebellious Baba Amr district was razed by the Syrian army in March. And fighting has broken out again between armed rebels and Syrian troops in the capital city of Damascus, once considered a safe pro-government stronghold. In all, 33 people were reported killed in Syria on Saturday.

This latest escalation of violence – plus at least two massacres of civilians in the past 10 days – makes plain, once more, that the ceasefire supposedly in place since 12 April under the Annan peace plan has failed utterly to stop the bloodshed. Against this backdrop, Russian foreign minister Sergei Lavrov's call for an international conference on reviving the Annan plan just looks like more stalling for time, as the Syrian dictator tries to crush his opposition.

Learn more: Nick Cohen's searing polemic in the Observer today has a stark and persuasive message: that Russia is playing western democrats for fools.

Take action: Sign Avaaz's petition to protect Syria's children by sending a 3,000-member UN force to shield civilian populations, and join our call to world powers to stop the merchants of death.