Tens of thousands of people demonstrated in cities across Europe, North Africa and the Middle East Saturday, shouting protests against the Israeli offensive in Gaza. And as the day dawned in Washington, several thousand protesters -- 10,000 according to organizers -- descended on the White House in support of Palestinians in Gaza. Protesters burned Israeli flags in Sweden and threw shoes at the US consulate in Edinburgh, Scotland. In central London, three officers were hurt when demonstrators hurled shoes and placards at police outside the Israeli Embassy. One officer was knocked unconscious. Veteran left-wing campaigner Tariq Ali, who had led the march, said: “The most appalling violence is happening in Gaza – a few punch-ups outside the Israeli embassy is neither here nor there.” But in Innsbruck, Austria, volunteer security personnel arranged by the Islamic organizers of a demonstration moved quickly to surround and protect an elderly man after he suddenly unrolled an Israeli flag in the middle of the protest. The 3,500 Innsbruck marchers carried banners calling for “Freedom for Palestine” and saying “Stop the Israeli Terror.” Israel says its 2-week-old offensive is intended to stop Palestinian Hamas rocket attacks on southern Israel. Palestinian medical officials say more than 800 people have been killed. In Washington, thousands of people gathered from about 1:00 P.M. (1800 GMT) in Lafayette Park, across from the White House, chanting “free Palestine” as others spoke from a podium. “There are many young people. We feel it's one of the most important demonstrations for Palestine ever in the US,” said Eugene Puryear, a coordinator of the protest, which was organized by the ANSWER (Act Now to Stop War and End Racism) coalition. Protesters waived Palestinian flags, wore keffiyeh -- a traditional Palestinian headdress -- and waived signs, some of which read “stop the Gaza holocaust” and “Free Palestine, let Gaza live.” They then led a march passing in front of the headquarters of The Washington Post newspaper to protest “its hard pro-Israeli line,” Puryear said, before heading to the offices of military contractor Lockheed Martin. “I came because there are innocent children dying daily in Palestine. The American people need to know the truth,” said 13-year-old Razan Ali, a Palestinian-American who bused in from New York. A crowd of 12,000 gathered in London's Hyde Park carrying placards marked “Gaza: Stop the massacre” and chanting “free, free Palestine.” Police said 15 people were arrested after a group of around 2,000 demonstrators clashed with police guarding the Israeli embassy. Two were detained on suspicion of assaulting police officers. Scores of marches were held across France, the biggest of them in the capital, where police estimated 30,000 people took part. Paris police scuffled with a small group toward the end. Police said a crowd of 5,000-10,000 demonstrated in Lyon, up to 4,500 in Marseille and 3,500 in Grenoble at the foot of the Alps. Police estimated that 30,000 people protested in the northern Spanish city of Barcelona, some carrying bloodstained blankets and mock dead bodies of children. The demonstration had been called by around 300 Catalan groups who have asked the Spanish government to back ceasefire initiatives and to stop all trade, especially arms, with Israel. In Italy, several thousand people carrying Palestinian flags marched in Milan, Florence and Venice to protest the Israeli offensive. In Milan, protesters burned a white sheet with the Star of David on it, and some participants carried posters with the Israeli flag and a swastika on them, the ANSA news agency reported. In Germany, some 8,500 people rallied in Berlin's Alexanderplatz and then marched to the city's main train station yelling slogans including “Israel and USA: the Intifada is back” and “Israel lets blood flow, Israel shoots innocents.” Hundreds of police were deployed along the Berlin demonstration route, and several Hamas flags were confiscated from the protesters. No serious incidents were reported, however, police said. In the western German city of Duisburg, 10,000 people marched. “We want to show our solidarity with the victims in the Gaza Strip, and signal our opposition to the oppression and violence in Gaza,” said organizer Engin Karahan. Protesters threw snowballs at two Israeli flags that hung from the windows of a house along the demonstration route, but otherwise no incidents were reported. In Norway, police used tear gas to try to disperse at least 1,000 protesters after some hurled bottles, rocks and fired fireworks at officers during a pro-Palestinian rally in the capital. Two people were injured during the rally, and two were taken into custody, said Oslo police spokeswoman Unni Groendal. Protesters in Sweden tried to break through sealed-off areas at Israel's embassy in Stockholm after a march through the city by 3,000 to 5,000 people. The crowd was dispersed after about an hour. Thousands of demonstrators in Edinburgh, Scotland, threw shoes at the American consulate – a gesture evoking an Iraqi journalist who threw his shoes at President George W. Bush during a recent Baghdad visit. Organizer Ian Hood said the group was angry with the United States for failing to stop the bloodshed in Gaza. Smaller protests also took place in the northern English city of Newcastle and in Belfast, Northern Ireland. Pro-Palestinian demonstrators in Athens were joined by several Greek leftist groups to form a crowd of about 2,000 who marched to the Israeli embassy. Children wore T-shirts sprayed with fake blood and the crowd burned Israeli and American flags but no major incidents were reported.