Antiterrorist police in London have identified a mosque in the British capital that they claim is the site of a recruitment center for Muslim youths ready to undertake military training in Afghanistan and Kashmir. An unknown number of young British Muslims have already undergone training, according to an Islamic leader in London. The British government is conducting an urgent behind-the-scenes inquiry into activities at the Finsbury Park Mosque. It is also examining claims by Muslim activists that Britain's support for operation Desert Fox against Iraq is triggering terrorist retaliation by Islamic groups. A central figure in the police inquiries is Abu Hamza, a senior cleric and regular preacher at the north London mosque and leader of a group calling itself "Supporters of Sharia." In a television interview Jan. 11, Mr. Hamza said he supports violent actions if they are carried out "for the sake of God" and will "stop state terrorism by Britain and the United States." Omar Bakri Mohammed, an associate of Hamza's at the London mosque, later told London's Daily Telegraph newspaper that he had arranged for several young British Muslims to take military training courses overseas. Early last month, the group's Web site advertised an "Islamic camp" being held at the mosque from Dec. 24 to 26. Hamza says the camp, attended by 30 youths, was intended to "distract them from television and the obscenity of Christmas." The ad said the camp would offer "military training for brothers, self-development skills, martial arts, map reading, etc." The extensive Web site, decorated with pictures of hand grenades, includes a 17-page "declaration of war" against the US by Osama bin Laden. The terrorist leader, based in Afghanistan, is suspected of masterminding last year's bomb attacks on the American embassies in Tanzania and Kenya that killed 224 people. THE bin Laden declaration includes the words: "The walls of oppression and humiliation cannot be demolished except in a rain of bullets." Threats by suspected bin Laden sympathizers prompted closure of US outposts in Cameroon and Botswana last week. On Jan. 11, officials extended closure of the US embassy in Uganda, a day after the US ambassador received a threatening call on her private cell phone. The British Embassy, located in the same complex in Kampala, also shut its doors temporarily. Existence of the London recruitment center has been highlighted by a diplomatic row that broke out last month between Britain and Yemen over the killing of three British tourists and one Australian held captive by Yemeni kidnappers. The hostages - members of a group of 16 - died when Yemeni security forces, acting against the advice of British diplomats, stormed the kidnappers' hideout. The dispute escalated last week when British newspapers reported that shortly before Christmas, Yemeni police had arrested five Muslim youths traveling on British passports. Yemeni officials say they were suspected of planning to carry out terrorist attacks on targets in Yemen. The youths are still being detained. Since their arrest a British oil worker has also been seized by Yemeni kidnappers. In this week's TV interview, Hamza confirmed that one of the youths is "probably" his stepson. Yemeni police say another British Muslim, who so far has escaped arrest, is Hamza's natural son. British security authorities have long known that there is a radical element among the United Kingdom's Muslim community, but they say the vast majority of British Muslims are law-abiding citizens. A Scotland Yard spokesman said Jan. 12 that London police were "aware" of Hamza and his activities, but declined to elaborate. According to government statistics, there are between 1.5 and 2 million Muslims in the UK. There are more than 600 mosques around the country, with thriving Muslim communities in Liverpool, Manchester, Leicester, Birmingham, Bradford, Cardiff, Edinburgh, and Glasgow. The five youths arrested in Yemen all come from Birmingham, in central England. Their families have told authorities the youths were vacationing in Yemen and insist they have no links to terrorist organizations. The families complain that the British government has been slow to make representations on the youths' behalf, but Foreign Secretary Robin Cook told the House of Commons this week that "every effort" was being made to find out the facts. Ghayasuddin Siddiqui, leader of a British Islamic umbrella organization calling itself a "Muslim parliament," said Jan. 12 that he rejected Abu Hamza and his political ideas. "I do not think many Muslims share his views," he said.