BBC News with Iain Purdon

The Turkish Prime Minister Recep Tayyip Erdogan has made his strongest denunciation yet of Syria's President Assad. "No regime," Mr Erdogan said, "can survive by killing and jailing its opponents." The Arab League has already suspended Syria for failing to implement an Arab peace initiative. Jonathan Head is in Istanbul.

The Turkish prime minister is habitually outspoken. Even so, his latest rebuke of President Assad, a man he considered a personal friend until a few months ago, was dramatic. "No regime," warned Mr Erdogan, "can survive by killing and jailing. No one can build a future on the blood of the oppressed." Turkey has now stopped cooperation on energy projects and says it's considering further sanctions which would not hurt ordinary people. Turkish business leaders say trade, which was worth around $2.5bn last year, has all but stopped.

Syrian opposition groups say as many as 70 people have been killed in the past 24 hours. The head of the main Syrian opposition movement, Burhan Ghalioun, says he has failed to persuade Russia to drop its opposition to international sanctions against Syria. Speaking after talks with Russian officials in Moscow, Mr Ghalioun described the talks as fruitful, although there was no change in the positions of either side.