More than 15,000 people joined an angry but peaceful protest in central London on Saturday against the Prophet Muhammad cartoons that have infuriated many in the Muslim world. Buses brought participants from cities around Britain to gather in Trafalgar Square, and they later marched through central London to Hyde Park, from where the crowd began dispersing late in the afternoon. "Free speech cheap insults," read some placards. "How dare you insult the blessed Prophet Muhammad?" asked another. Speakers shouted from the podium and the crowd yelled back as the demonstration grew increasingly angry. Police said about 15,000 people were present, and there were no reports of violence or arrests. Organizers estimated 40,000 people marched. "Every Muslim understands this basic concept of the centrality in importance of Muhammad to their lives," said Taji Mustafa, a spokesman for the Muslim Action Committee, which organized the event. "So when he is demonized, the young and old are deeply affected. As long as the abuse is ongoing we will continue to rise up in protest." Mustafa said Muslims' anger had been fueled by several European newspapers' decisions to reprint the cartoon, which first appeared in a Danish paper in September, and recently by an Italian Cabinet minister's decision to wear a T-shirt showing the cartoons. Reforms Minister Roberto Calderoli's appearance in the shirt was blamed for sparking clashes that killed at least 10 people at an Italian consulate in Libya on Friday. He resigned from his post under pressure Saturday. Mustafa said the cartoons were reminiscent of attacks on Jews in European publications in the 1930s. "Now there is a demonization of the Muslim community, so we have to speak up to prevent something like the Holocaust from happening," he said. The protesters postponed their departure from Trafalgar Square to Hyde Park by nearly an hour so participants could take turns kneeling and praying on mats in a designated prayer area. During the march, the crowd was separated by gender, with men in the front and women behind. Some demonstrators wore traditional Muslim garb, including women covered in robes that left only their eyes exposed. Many others were in Western dress, such as jeans and sweat shirts. "What happened should not have happened," said Younas Yousas, 33, a protester from east London. "Their freedom of speech should be restricted because it hurts our religion. At the end of the day everyone needs to respect others' religions. And we should strive for peace." Demonstrators carried placards reading "Europe lacks respect for others," and "Don't they teach manners in Denmark?" The Muslim world has been outraged by the drawings, which have been reprinted in European papers in recent weeks in the name of press freedom. The tension has noticeably increased anti-Western sentiments in the Muslim world. Two weeks ago, protesters in London carried signs with extremist slogans including "Europe, you will pay. Your 9/11 is on its way," and "Behead the one who insults the prophet." One demonstrator at that protest, Omar Khayam, 22, dressed as a suicide bomber. He publicly apologized later, but was arrested for breaching parole.