Protesters tore up images of Syria's President Bashar Assad as hundreds of British Muslims gathered to support the Arab Spring.
Around 600 demonstrators marched to the Syrian Embassy in London's exclusive Belgravia district where they called for Assad and Libyan dictator Colonel Gaddafi to immediately step down.
Some of the demonstrators repeatedly hit large posters of Assad and Gaddafi with shoes - a hugely insulting gesture in the Arab world. Others ripped apart poster images of Assad, brandishing the torn remnants at the building.
Around 600 civilians and 100 soldiers have been killed since the Syrian revolt began, human rights groups have said.
Protesters from Leeds, Bradford, Luton and other parts of the UK gathered together to call for the end to the violence in Syria, Yemen and Libya as the Arab Spring escalates.
The uprisings have swept through other countries in the Middle East and North Africa, including Egypt and Tunisia. Protesters called for democratic and accountable governments to be installed in the countries that have managed to overthrow their leaders.
Taji Mustafa, a marcher from the Muslim political group Hizb ut-Tahrir, called for a caliphate - a single state for Muslims - to be installed in the liberated countries. He said: "People are here from all over the UK to show solidarity and support to those who are bravely standing up against tyrants across the Muslim world.
Hizb ut-Tahrir regards the caliphate as the ideal form of government because it follows what it believes are the laws of God as set out in the Koran, rather than laws designed by man. Mr Mustafa added: "All of these Western-backed tyrants have to go."
The march snaked through central London with male demonstrators at the front and the women protesters bringing up the rear.
Many carried banners bearing slogans such as "Stop US imperialism, support a caliphate" and "Arab puppet rulers must go".