In Greece thousands of demonstrators took to the streets of Athens chanting "we'll stop the war" and splashing red paint on the front windows of a McDonalds restaurant. The crowd of some 15,000 protesters then marched to the US embassy.
Authorities have tightened security at potential targets in the Greek capital after a spate of arson attacks against US banks and other businesses since the war began.
In the southern German city of Stuttgart thousands of demonstrators encircled the US military's European Command, linking hands in a human chain amid a new round of nationwide protests against the war in Iraq.
About 6,000 people formed a three-mile chain around the facility's perimeter, which stayed in place for five minutes. They were watched over by several hundred police officers, but no incidents were reported.
Meanwhile in Cape Town, South Africa, thousands of anti-war protesters chanting slogans and burning American flags demanded US, British and Spanish ambassadors be expelled from the country.
Lawmakers, activists, trade union members and religious groups joined the march of more than 10,000 protesters to the US Consulate, the South African Press Association reported.