European intelligence officials say the streets of Milan are the epicenter of a network of al-Qaida and other extremists recruiting militants from Europe, to kill Americans in Iraq.

Intelligence experts estimate hundreds of volunteers or recruits from Europe have attempted to enter Iraq.

One British Olympic hopeful in martial arts reportedly blew himself up in a suicide attack in Iraq last month.

At least five Muslims from Italy also are believed to have been killed carrying out attacks in Iraq, according to a confidential Italian court document obtained by NBC News. Another Italian recruit was tied to the rocket attack on the Baghdad hotel where Deputy Defense Secretary Paul Wolfowitz was staying.

“The most troubling picture is the fact that the network is extremely complex and well organized, and branches throughout Europe,” according to European terrorism expert Lorenzo Vidino.

Police in three countries recently arrested nine suspects, including four men, for allegedly providing false documents and logistical support through a network that spans Britain, Norway, France, Spain, Germany and Italy.

“Militants from all over Europe were basically calling the cell in Milan to find a way to cross the border in to go to Iraq,” Vidino added.

Syrian connection

Most went by way of Syria. In wiretapped phone calls detailed in the Italian documents, a militant in Syria asks for recruits similar to the Japanese Kamikaze pilots of World War II.

One another call, a ringleader in Milan tells his partner in Syria, “I am going to send you four more.” The man in Syria responds, “We need 40 of them, but good like those of last time.”

And in an intercepted call last March, a true believer in Italy boasts, “Many communities... have gotten ready to leave and fight against the Americans... Their blood is hot.”

British peace envoy Canon Andrew White says he recently encountered British Muslims about to enter Iraq and was stunned by who they were. “They didn’t have long beards," he said. "They were very smart. They spoke very good English. And they were the least likely people that you would expect to be involved in any terrorist activity."

German intelligence reports much of the recruiting has shifted from mosques to Internet chat rooms and coffee houses.

“These extremists are even more cautious, even more clandestine than before. They are more careful,” according to intelligence official Carl Heinrich von Bauer of Germany’s North Rhein-Westphalia state.

NBC News obtained a flier by a Milan group called “Lovers of Martyrdom” which says, “Leave this short meaningless life and expect the highest rewards in heaven... The doors are open for new recruits... Many volunteers have entered Iraq thru Syria.”

There are no reliable numbers on how many European militants are actually fighting in Iraq. The U.S. military says foreign fighters are only a fraction of insurgents who’ve been caught. Still, their presence can only make the violence worse.