Islamic extremists accused of plotting to kill Iraq's prime minister in Germany are smuggling battle-hardened fighters from Iraq to Europe, raising a potential new terrorist threat on the continent, according to German officials. More than 20 alleged supporters of Ansar al-Islam have been arrested in Europe in the past year as authorities move against the group that has links with al-Qaida and Jordanian terrorist Abu Musab al-Zarqawi, who's been leading bloody attacks against U.S. forces in Iraq.Ansar al-Islam is suspected of spiriting dozens of fired-up young Muslims to Iraq to join the insurgency, but the latest raids in Germany — the most spectacular yet against the group — heightened concerns that the organization also could pose a menace outside Iraq, too. Acting on intelligence suggesting the group planned to attack Iraqi Prime Minister Ayad Allawi in Berlin, police on Dec. 3 arrested three Iraqis believed to be Ansar al-Islam members. Arrest warrants for the three plot suspects — identified only as Ata R., Mazen H. and Rafik Y. — were based on wiretaps and intelligence that one of them apparently cased Berlin locales on Allawi's itinerary. But investigators have turned up no weapons or bomb-making materials, and Allawi's name was never mentioned in the men's coded telephone conversations.