A reported massacre in Syria is a fresh reminder of the "callous brutality" of the Assad regime, Foreign Secretary William Hague said as he continued a push for a tougher European Union stance.
As many as 85 civilians including women and children are said to have been killed in the Damascus suburb of Jdaidet al-Fadl as part of a major offensive by government forces against opposition-held territory in the capital.
The Foreign Secretary - who with France is pushing for the lifting of an arms embargo to allow rebel forces to be supplied with weapons - said he would raise the issue with EU foreign ministers meeting in Luxembourg.
"I am appalled by the reports of the killing by Syrian government forces of dozens of people, including women and children, in the town of Jdaidet Al-Fadl, a suburb of Damascus," he said.
"This is yet another reminder of the callous brutality of the Assad regime and the terrible climate of impunity inside Syria.
"It underlines the urgent need to bring the conflict in Syria to an end.
"At the Friends of Syria Core Group meeting with the Syrian opposition National Coalition in Istanbul we agreed to redouble efforts to reach a political resolution and increase support to the opposition, and I will be discussing these efforts with European foreign ministers today."
The US announced at the weekend that it would double aid to the opposition but did not meet rebels' calls for weapons and military intervention to halt the two-year violence which has killed more than 70,000 people.