CAIRO, Egypt — A group calling itself "The Secret Organization of Al Qaeda in Europe" has posted a claim of responsibility for the series of blasts in London, saying they were in retaliation for Britain's involvement in Iraq and Afghanistan. The statement was published on a Web site popular with Islamic militants, according to Der Spiegel magazine in Berlin, which republished the text on its own Web site. "Rejoice, Islamic nation. Rejoice, Arab world. The time has come for vengeance against the Zionist crusader government of Britain in response to the massacres Britain committed in Iraq and Afghanistan," said the...