BERLIN, Germany — A U.S. intelligence intercept of suspicious communications between Pakistan and Stuttgart was the initial break that ultimately led to the arrest this week of three suspected Muslim militants accused of plotting massive car bomb attacks here against Americans, U.S. and German officials said Thursday.
The communications detected last year referred to apparent terrorist activity, the German and U.S. officials said in interviews. The German officials characterized the communications as specific and alarming. All the officials asked to remain anonymous because they were not authorized to discuss the case publicly.
American authorities passed the lead to German police, who conducted a painstaking investigation that led to the arrests of the three suspects, two of whom are German converts to Islam. Police here suspected that militants were communicating with Pakistan from an Internet cafe, a frequent strategy to avoid detection, but they did not know which one. So they deployed surveillance teams at several dozen Internet cafes around the city, officials said.
The stakeouts paid off when police spotted a 28-year-old convert who was already known as an associate of Islamic militants and has been identified as Fritz Gelowicz.
Arrested this week with the two other suspects, Gelowicz was described Thursday by anti-terrorism officials as the lead figure in a group that learned bomb-making at an Al Qaeda-linked training camp in Pakistan last year. The three are accused of plotting to kill Americans at or near military bases and airports in Germany with the equivalent of more than 1,000 pounds of TNT. The third man jailed is a Turk who has been living in Germany.
On Thursday, police pressed their investigation of at least seven other suspects, including several who are believed to have left the country.
About 300 investigators worked round-the-clock for nine months to monitor the alleged plotters. Using sophisticated eavesdropping equipment of their own, the Germans watched and listened as the suspected cell coalesced and amassed a stash of bomb-making materials.
When they announced the arrests Wednesday, German authorities said they had focused on Gelowicz after he was briefly detained in January on suspicion of scouting a U.S. military barracks. But in reality, Gelowicz and his associates already had been identified as an urgent threat, thanks to the American intercepts last year, according to officials in Germany and the U.S.
"The U.S. counter-terrorism community supported efforts to draw links, to do intercepts and to monitor communications between Pakistan and Germany," a U.S. counter-terrorism official said.
The counter-terrorism official described the initial intercepts as "a key factor" that "helped build the case."
"It led to a very long period of surveillance, and the arrests." The official said the intercepts continued throughout the investigation.
This year, U.S. intelligence agents intercepted a key communication in which militant handlers in Pakistan asked for an update on the plot and pushed the suspects to move faster, German officials said.
At the start of the investigation, American intelligence also helped German police focus on the second convert, Daniel Schneider, a German official said.
U.S. intercepts detected the 22-year-old convert's e-mail communications with Pakistan and guided German police to him through a wireless signal he was pirating, officials said.
The suspects were simultaneously stealthy, brazen and reckless, officials said. The three evidently became aware of the constant surveillance and tried to thwart it, changing trains and dodging tails. They may also have noticed that the German and U.S. governments had issued several warnings during the year about increased terrorism risks, particularly threats posed by militants trained in Pakistan.
But when police this year confronted Schneider, and warned him that they knew what he was up to, he brushed them off, a German anti-terrorism official said. The trio plunged zealously ahead, the official said, apparently eager to die.
The suspects wanted to kill as many Americans as possible in the process, officials said. Probable targets of their alleged plan to build three car bombs were crowded bars, nightclubs, restaurants and airports. They chose Germany because it was their home turf and because of the large population of Americans around military bases.
"It's not just the military, but Americans in general," said a law enforcement official who asked not to be identified. "If they could have wiped out 1,000 American tourists, they would have been happy."
The three were unemployed; the two German natives collected welfare. Authorities said the trio claimed allegiance to the Islamic Jihad Union, an Uzbek group that in 2002 broke off from the Islamic Movement of Uzbekistan, an Al Qaeda ally. The IJU ran the Pakistani camp where they trained and oversaw their alleged mission, officials said.
Unlike cases such as the London transportation bombings of 2005, in which the bombers communicated frequently with masterminds in Pakistan during the final weeks, the cell here was largely "self-contained and self-directed," the law enforcement official said. "They seemed to be running their own show."
The third man arrested in a police raid at a vacation home in central Germany was identified as Adem Y., 29.
The cell appears to have brought together separate groups connected with the two converts, officials said.
Gelowicz and another suspect of Turkish origin were active in radical circles in Stuttgart and the nearby town of Ulm, a hub for emerging networks sending aspiring Islamic militants to Pakistan, authorities said.
Schneider and two other suspects are from Saarland, a small state near the French border. Schneider turned radical four years ago and studied at Koranic schools in Syria and Egypt, officials said.
The suspects from Saarland include a Lebanese man who arrived in Germany on Monday after being deported from Pakistan, where he allegedly was en route to a terrorist training camp, officials said. The suspect was released after questioning this week but remained under investigation. Another man at large is Zafer S. a Turk believed to be in Turkey or Iraq.
Even if the missing suspects are arrested, prosecuting them might be difficult. It is not a crime in Germany to attend a foreign terrorist training camp.
U.S. and German officials are also still working to piece together the process by which the suspects joined up with the Islamic Jihad Union, also known as the Islamic Jihad Group.
Also troubling to officials was the presence of several suspects from Germany's vast Turkish community. In the past, Germans of Turkish origin have been far less likely to turn up in Islamic extremist networks than Pakistani Britons or young North Africans in France and its neighbors to the south.