Hamburg, Germany (CNN) -- A group of jihadists from the German city of Hamburg are alleged to be at the heart of the recent al Qaeda plot to launch co-ordinated terrorist attacks against European cities, according to European intelligence officials.
The plan prompted the U.S. State Department to issue a Europe-wide security advisory for Americans traveling in Europe.
Japan issued a similar alert Monday, citing the warnings issued by the United States and by Britain, which raised the level highest for France and Germany.
Western intelligence officials say they learned about the plot when Ahmed Sidiqi, a German citizen of Afghan descent was arrested in Afghanistan in July and taken to the U.S. airbase at Bagram for questioning. He has not been charged and intelligence sources in Germany say he is co-operating with the investigation.
In early 2009, Sidiqi and 10 others left Hamburg for the tribal areas of Pakistan -- where most joined a jihadist group fighting U.S. and coalition forces across the border in Afghanistan, according to German intelligence officials.
Sidiqi told American interrogators that at least one member of his travel group was to be a "foot-soldier" in the plot, with other members of the group helping to plan the attacks, a European counter-terrorism official told CNN.
CNN
