Protected by a massive police cordon, pro-Israeli groups rallied in London and Manchester on Sunday, a day after violent clashes erupted at an anti-Israel demonstration opposite the Israeli Embassy. Some 5,000 people stood with Israel in Trafalgar Square in London and 3,000 at Albert Square in central Manchester calling for "peace for the people of Israel and Gaza" and an end to "Hamas terror." "The basic simple goal of the people of Israel is to be allowed to live in peace, without violence, without fear and without terror," Ambassador Ron Prosor told the crowd in London. "We tell the terrorists enough is enough. They, and not us, will be defeated." The London rally almost fell victim to a hoax e-mail stating that it was canceled. However, community organizations put on a mammoth effort that included phone calls, e-mails and messages over the social networking site Facebook to make sure people knew it was going ahead. The e-mail claimed to be from the Board of Deputies of British Jews, the representative organization of Anglo-Jewry and one of the organizers of Sunday's rally. A community leader who asked not to be named told The Jerusalem Post that an arrest has been made. Police confirmed they were looking into "an allegation of a malicious e-mail communication" but could not confirm an arrest. The hoax e-mail said that the Board of Deputies, in consultation with other Jewish organizations had decided to cancel the rally "after intense discussions within the community, due to a feeling that such a demonstration would not be in accordance with the board's wish to bring the conflict to an immediate conclusion." It claimed that the board had called for an immediate cease-fire and for Israel to negotiate with Hamas. "The board stands in solidarity with the besieged and injured people of Gaza, as well as the victims of terrorism in Israel, and we oppose all violence as contrary to the tenets of the Jewish religion," the fraudulent e-mail said. "We would like to reach out to the British Muslim community, as well as those of no religion who have demonstrated against Israel's military campaign. We share your anguish at the destruction and loss of life caused and hope that our action in calling off our demonstration will be a small step towards peace." There was a 1,000 strong counter-protest in London, where mainly Jewish anti-Zionist groups and Muslim protesters carried placards saying: "We are all Hamas" and "Stop the Holocaust in Gaza." At the end of the rally, sections of both sides remained behind and taunted each other - police allowed this to happen for around 20 minutes before moving the demonstrators on. There was also a small counter-demonstration in Manchester. No trouble was reported. On Saturday, protesters marching from Hyde Park in central London to the Israeli Embassy waved Hizbullah and al-Qaida flags and chanted "Hey, ho, Israel has gotta go" and "From the river to the sea, Palestine will be free." Many held placards with Nazi analogies such as "Gaza = Warsaw Ghetto," "Gaza: NaZionist death camp" and "Stop the Holocaust in Gaza." At the embassy, masked protesters pushed over crowd control barriers, threw things at police and set off firecrackers and fire extinguishers. Shop windows were smashed and pieces of broken window were thrown at police. Police reported that three officers were injured, including one who was knocked unconscious, and at least 15 arrests were made. Meanwhile, a group of prominent Jewish community members has called on Israel to cease its military operation in Gaza, saying that only negotiations can secure Israel's security. In a letter in Sunday's Observer newspaper, a group of rabbis, and Jewish academics and politicians - that includes Sir Jeremy Beecham, former chairman of the Labor Party; Baroness Julia Neuberger, a rabbi and the Liberal Democrat whip in the House of Lords; head of the Reform Movement Rabbi Dr. Tony Bayfield; and the chief executive of Liberal Judaism, Rabbi Danny Rich - warned that Israel's action will "strengthen extremism." "We are concerned that rather than bringing security to Israel, a continued military offensive could strengthen extremists, destabilize the region and exacerbate tensions inside Israel with its one million Arab citizens," the letter stated. The signatories, who describe themselves as "passionate supporters of Israel," also wrote that Israel has a right to defend itself, calling Hamas's actions a "war crime." However, they said Israel's actions threatened to undermine international support and that "now only negotiations can secure long-term security for Israel and the region." Meanwhile, Canadian author Naomi Klein has called for a boycott of Israel. Writing in the Guardian newspaper's blog, "Comment is Free," on Saturday, she said the best strategy to "end the increasingly bloody occupation" is for Israel "to become the target of the kind of global movement that put an end to apartheid in South Africa." "Economic sanctions are the most effective tool in the nonviolent arsenal: surrendering them verges on active complicity," Klein wrote.