A spokesman for the Syrian community in Austria, Amer Alkhatib, said around 600 people carrying Syrian and Kurdish flags took part in the protest, while police put the numbers between 200 and 300.

"Kurds and Arabs, Muslims and Christians, Druze and Yazidi have gathered here in order to demonstrate against the Assad regime," Syrian Barakat Haj told the Austria Press Agency.

The protestors handed out leaflets and chanted anti-Russian and anti-Chinese slogans after their veto of a UN Security Coucil resolution on Syria last week, marching from the Vienna State Opera to the Russian and Syrian embassies.

Around 20 people stormed into the Syrian embassy overnight on Saturday in central Vienna, demonstrating on the balcony while people outside cheered. Some damage was caused and police detained 11 people.

A violent crackdown on anti-regime protests that broke out in March across Syria has killed more than 2,900 people, according to the United Nations. Three people were shot dead in the central city of Homs on Tuesday, activists said.