German police on Friday arrested three suspected members of the al-Qaida terrorist organization who officials say posed a "concrete and imminent danger" to the nation.
Authorities did not say whether the three had planned specific targets and offered few details, but security officials said that all three suspects were German nationals of Moroccan origin. They also said that two were arrested were in the western German city of Duesseldorf and one in nearby Bochum. The arrests were based on suspicion they were planning a terror attack, they said.
U.S. officials told NBC News the arrests are significant because while other recent arrests have been of radicals inspired by al-Qaida, at least one of the three nabbed Friday was trained by the militant organiation in the tribal areas along the Pakistan-Afghanistan border.
The three men had been under surveillance for "some time," said one official. The men had already put together "precursor chemicals" for an attack and were planning to have a "test run" on Friday morning, officials told NBC News. Although the test was postponed, German authorities decided to move in and arrest them.
U.S. officials called the target "localized" and related to "public transportation, trains or buses." The official would not comment when asked if U.S. servicemen might have been targeted.
"This was well beyond aspirational," said the U.S. official. "The police had been watching for some time, watching and monitoring, planning on disrupting it at the right time."
Asked if this plot was behind the general alert in Germany last summer and fall, the official said the alert was "generated by these types of plots," but not specifically this plot. "We are seeing these in Europe every few months," he added.
The arrests "succeeded in averting a concrete and imminent danger, presented by international terrorism," German Interior Minister Hans-Peter Friedrich said in a statement. They showed "Germany remains a target of international terrorists."
There was no indication Friday's arrests had any link to yesterday's bomb attack in Morocco that killed 15 people in a crowded tourist cafe.
Germany has escaped any large-scale attack by an Islamic terror organization, such as the Madrid train bombings of 2004 and the London transit attacks of 2005. But Germany's presence as part of the NATO coalition in Afghanistan has sparked anger and at least two major plots have been thwarted or failed in Germany before they could be carried out.
The suspects had been under surveillance since November when Germany increased security across the country in response to heightened terror threat warnings in Europe, but authorities only had enough evidence to launch an official criminal investigation starting April 15, Friedrich said in a statement.
Federal prosecutors said earlier they had ordered Germany's federal police to arrest the trio, but gave no further information about the timing or location of the arrests. Officials were planning a news conference for Saturday.
A U.S. official speaking on condition of anonymity in order to discuss an ongoing investigation told The Associated Press in Washington, D.C., that a SWAT team picked up three people in a raid on suspicion they were planning an attack with explosives.
"Our concerns about threats in Europe had a number of different threads and strands, some of which have been disrupted by good intelligence and law enforcement work by the relevant services," another U.S. official told the AP.
"There have been five disrupted plots in Europe during the past four years — including a credible plot in Germany in 2007 — all of which demonstrate Pakistan-based al-Qaida's steadfast intent to attack the US and our allies."
Duesseldorf, a city of 600,000 has one of the largest Moroccan immigrant communities in Germany. It is to host the Eurovision Song Contest on May 14, which is expected to draw hundreds of thousands of spectators.
The German prosecutors said the three alleged terrorists would be brought before a judge Saturday who will decide whether they are to remain in detention pending a trial.
Germany raised its security posture in November after receiving information from its own and foreign intelligence services that led authorities to believe a sleeper cell of some 20 to 25 people may have been planning an attack inside the country or in another European nation.
Around the same time Germany also received information from U.S. sources that an attack similar to that in Mumbai in Nov. 2008 that killed 166 may be planned for Germany, the official said. Later, Germany received information on possible attacks at Christmas or New Year's.
In February, the German government lowered the terror level and reduced the number of police officers patrolling railway stations and other public places, but made clear at the time that a threat to the country still remains.