The Arab League chief, meanwhile, warned that failure of the peace deal agreed this week would be catastrophic and demanded an immediate end to the bloodshed.

To mark the Muslim feast of Eid al-Adha, Damascus freed 553 people arrested during protests while also condemning Washington for suggesting Syrians reject an amnesty offered to lay down their arms.

The Arab League plan calls for an end to violence, the release of those detained, the withdrawal of the army from urban areas and free movement for observers and the media, as well as talks between the regime and opposition.