German authorities arrested a suspected member of the al Qaeda network in a late night raid at a four-star hotel in Moenchengladbach.
The unarmed man, who had an Italian name, was charged with membership of an illegal organization, authorities said.
Federal authorities had tipped local police about three wanted men but only one was found during a large operation late last night, said Moenchengladbach police spokesman Mr Michael Gutze.
"We are still checking his identity. This may take until morning," he said. "By appearance he appears to be between 30 and 40-years old."
German authorities have conducted a massive investigation into possible links to the September 11 attacks on the World Trade Center after it emerged that Mohamed Atta and other hijackers had lived in the northern city of Hamburg for years.
Authorities are also investigating the arrested man's travel plans and other details. Moenchengladbach, with a population of 270,000, is near Duesseldorf in western Germany.
"He checked in alone today at 2 p.m.," Mr Eddie Adam, night manager at the Dorint Hotel, said after midnight. "Then we received a tip from the federal criminal authorities who came at around midnight."
"Police are still here checking rooms."
Earlier yesterday, police in Bremen searched the apartments of a Lebanese and a Tunisian suspected of membership of an illegal organization, although no arrests were made, officials said.