Thousands of chanting, banner-waving demonstrators marched in cities across Europe on Saturday to demand a halt to Israeli bombing in the Gaza Strip. Protests were held in Britain, France, Germany, Greece, Ireland, Italy, the Netherlands, Spain and Turkey as the Israeli offensive entered its second week, and before Israel confirmed ground forces had entered Gaza. Israeli Arabs held a protest march, Kuwaitis also took to the streets, a day after bigger Middle East rallies, and peaceful pro- and anti-Israel protests were held in New York. In Paris, police said more than 21,000 demonstrators, many wearing Palestinian keffiyeh headscarves, marched through the city center chanting slogans such as "Israel murderer" and waving banners demanding an end to the air attacks. Groups of protesters clashed with police. At least three cars were set alight and about 20 overturned by demonstrators as the march ended near some of the biggest department stores in the French capital. In London, police said more than 10,000 people staged a march and rally to urge an end to the Israeli offensive against Hamas militants that has killed at least 446 Palestinians. Similar protests were planned in some 30 other towns. In many cities people waved shoes -- recalling the action of an Iraqi journalist who hurled footwear at U.S. President George W. Bush in Baghdad last month in a symbolic insult. British demonstrators threw dozens of shoes into the street as they passed the gated entrance to Downing Street, where Prime Minister Gordon Brown lives, and shouted angrily at a line of 40 police officers on guard there. "Come to get your shoes Gordon," one woman shouted as other marchers directed chants of "Shame on you" at Brown. A spokesman said Brown had spoken again to Israeli Prime Minister Ehud Olmert on Saturday and was pressing hard for an immediate ceasefire. Leading the march were singer Annie Lennox, politicians Tony Benn and George Galloway and comic Alexei Sayle. Demonstrators carried Palestinian flags and placards with slogans such as "End the siege on Gaza" and "Stop the massacre."