Thousands of Canadians joined demonstrators around the world Saturday in a series of heated protests against Israel's offensive in Gaza, with scuffles and arrests reported in several European cities.

Outside the Israeli Consulate in Toronto, police estimated about 2,000 people gathered in frigid weather to condemn the Israeli attacks, while a smaller group of pro-Israeli demonstrators made their presence known behind a police barricade.

Protestesters stamp on a burning Israeli flag Saturday during a demonstration in Montreal calling for an end to Israel's offensive in Gaza. (Graham Hughes/Canadian Press)In Montreal, about 1,000 marched in a protest organized by several large labour federations in support of the Palestinian people of Gaza. A crowd set at least one Israeli flag on fire.

In Vancouver, hundreds of people gathered in the pouring rain in front of the city's art gallery, where the protest spilled on to a downtown street and stopped traffic.

Protesters waved placards and chanted "Free Gaza" as speakers condemned Israel.

Scores of marches were held across France. The biggest was in Paris, where an estimated 30,000 people took part and scuffles with police were reported.

In Washington, hundreds rallied near the White House and the hotel of president-elect Barack Obama to demand an end to the Israeli military campaign.

Israel says its two-week-old offensive is intended to stop the Hamas militant group from launching rocket attacks on southern Israel. Medical officials say more than 800 Palestinians have been killed.

Thirteen Israelis, most of them soldiers, have also been killed since the conflict began on Dec. 27.

Protesters burned Israeli flags in Sweden and threw shoes at the U.S. Consulate in Edinburgh, Scotland.

Riot police face protesters against Israeli military action in the Gaza Strip, near the Israeli Embassy in London on Saturday. (Akira Suemori/Associated Press) In central London, two officers were hurt when demonstrators attempted to topple barriers outside the Israeli Embassy and clashed with police. One officer was knocked unconscious as protesters shattered shop windows with projectiles and sticks.

In Innsbruck, Austria, volunteer security personnel arranged by the 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.

A crowd of 12,000 gathered in London's Hyde Park carrying placards marked "Gaza: Stop the massacre" and chanting, "Free, free Palestine."

In Italy, several thousand people carrying Palestinian flags marched in Milan, Florence and Venice to protest the Israeli offensive.

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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. Hundreds of police were deployed along the 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 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.

Nearly 20,000 people marched through the southern Lebanese town Nabatiyeh in a protest organized by Hezbollah, an ally of Hamas that fought its own 34-day conflict with Israel in the summer of 2006.

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. Two people were injured and two were taken into custody, said Oslo police spokeswoman Unni Groendal.

With files from the Associated Press and the Canadian Press