Syrian demonstrators ransacked their country's embassy in Cairo and broke into the missions in London and Kuwait, part of protests around the world against the worst bloodshed of the 11 month uprising against President Bashar al-Assad.
The Cairo crowd smashed furniture and equipment and set fire to parts of the embassy building overnight.
In London, about 150 people hurled stones at the Syrian embassy, smashing windows and shouting slogans. Five men were arrested after breaking into the building and another was held for assaulting police, London police said.
Syrian residents in Kuwait broke into the embassy there at dawn on Saturday, tearing down the flag and injuring several security guards, state news agency KUNA reported.
Rallies also broke out outside Syrian embassies in Germany, the United States and Greece after human rights activists reported more than 200 people were killed in shelling by government forces in the city of Homs.
The gate of the embassy in central Cairo was broken and furniture and computers were smashed on the second floor of the building. Parts of the first floor were burned.
The scene was calm by early Saturday morning and Egyptian police were guarding the embassy. Embassy official Ammar Mohamed said he had been told by security officials about the overnight attack and arrived at the site to assess the damage.
Hundreds of demonstrators gathered at a police station a few streets away to demand the release of as many as 11 Syrians and an Egyptian who they said were detained during the protest at the mission.
God you are so strong, help us secure victory over Bashar, chanted protesters outside the Cairo police station where they said the detainees from the demonstration were taken.
At the United Nations, the Security Council was due to meet later in the day to vote on a resolution on Syria.
A live internet stream from the Washington rally showed dozens of people shouting Syria soon will be free.
Meanwhile in Athens, 12 Syrians and one Iraqi were detained for throwing stones at a guard post outside the Syrian embassy, a Greek police official said. They were expected to be released later in the day.
Syrians have held regular protests outside the Cairo headquarters of the Arab League, which has suspended Syria's membership, imposed sanctions and sent Arab monitors to Syria to assess whether the government was heeding an Arab peace plan.
The League called on Assad to step aside and hand powers to a deputy to start a dialogue with the opposition. Arab officials have travelled to New York to seek U.N. Security Council backing for the resolution.
(Additional reporting by Angeliki Koutantou in Athens and Michael Holden in London; Writing by Edmund Blair; Editing by Maria Golovnina and Peter Graff)