Tens of thousands of demonstrators marched in cities across Europe and the Middle East on Saturday to protest against Israel's offensive in Gaza, with sporadic clashes with police as some rallies turned violent.

Police in riot gear confronted around 20,000 protesters waving banners and Palestinian flags outside the Israeli embassy in central London, while Oslo police used tear gas as they fought activists on the streets of the Norwegian capital.

About 30,000 took to the streets of Paris to call for an end to Israeli attacks in Gaza, with many demonstrators wearing Palestinian keffiyah headscarves and chanting "We are all Palestinians," "Israel murderer" or "peace."

"We are here to demand the end to this unacceptable war. There are more than 800 victims including numerous children and civilians. We cannot accept that," said Communist Party leader Marie-George Buffet at the Paris march.

More than 10,000 people took part in a demonstration in London on Saturday against Israel's offensive in the Gaza Strip.

Some of the protestors threw shoes at police, burned placards and tried to break through barriers.

Police said 12,000 people took part in the march from Hyde Park to the Israeli embassy, while media reports spoke of tens of thousands.

Protests also took place in Belfast, Edinburgh, Aberdeen and Newcastle.

Jewish organizations plan to hold peace demonstrations in London on Sunday.

London's former mayor Ken Livingstone, musician Brian Eno and singer Annie Lennox were among those who supported the protest Saturday.

Livingstone said the British government and the European Union should push Israel to "stop the carnage."

Over the last week, thousands in various British cities have been protesting the conflict, hurling shoes at the iron gates in front of Downing Street.

Nearly 20,000 people marched through southern Lebanon on Saturday to protest Israel's Gaza operation, as thousands also took to the streets in several European cities to show their anger.

Similar protests have occurred almost daily in the Middle East and elsewhere since Israel launched its operation more than two weeks ago to stop rocket fire from the militant Palestinian group Hamas. The demonstrations have been fueled by the rising death toll in Gaza, which currently stands at over 800 Palestinians. Thirteen Israelis have died in the fighting.

Saturday's rally in the southern Lebanese town of Nabatiyeh was organized by the militant Hezbollah group, a strong ally of Hamas that fought its own war with Israel in the summer of 2006.

The thousands of demonstrators who marched through the streets waved Lebanese and Palestinian flags and some carried posters of bloody Palestinian children. Gaza is the nation's battle, read a banner carried by several of the protesters.

Thousands of people also protested in several cities across Europe, with the largest crowds in Germany, where some 20,000 took to the streets in Berlin and two other cities.

An estimated 8,500 rallied at Berlin's Alexanderplatz and then marched through downtown to the city's main train station. Some 10,000 people also marched in the western city of Duisburg, calling for an immediate end to the violence and a lifting of the blockade of Gaza. They carried signs with slogans like "Freedom for Palestine" and "Down with the murdering of children."

Thousands of demonstrators in the Scottish capital of Edinburgh gathered in front of the American consulate to toss shoes at the 19th century town house. Sky News television footage showed police recoiling as a storm of shoes flew over their heads.

"They were just flying, like hail through the sky," protest organizer Ian Hood said in a telephone interview. He said protesters were angry at the U.S. for failing to stop the bloodshed in Gaza.