Germany, which has forces stationed in Afghanistan, has been on high alert for attacks. The country has feared a re-emergence of militant Islamist groups since 2001, when the northern city of Hamburg was used as a base for planning the Sept. 11 attacks.
In April the U.S. embassy in Berlin announced it was boosting security at diplomatic and military facilities in Germany in response to an increased threat of terrorism there.
RAID ON HOUSE
Ziercke said the men had been seized at a rented holiday house in the Sauerland region of North Rhine-Westphalia in western Germany.
Between February and August 2007, he said, the accused had acquired 12 large vats and filled them with a 35 percent hydrogen peroxide solution totalling some 730 kilogrammes.
"This amount would have been enough to cause damage on a greater scale than in London and Madrid," Ziercke said. He said the suspects were likely planning simultaneous car bomb attacks in locations across Germany.
Some 300 police had been tracking the suspects since December, when one of them was observed scouting out U.S. military facilities in the German city of Hanau, near Frankfurt.
The police swooped on Tuesday, raiding the house and some 40 other sites across Germany after local police unwittingly stopped the suspects on a routine traffic violation several days ago and they grew nervous, Ziercke said.
One suspect escaped out of a bathroom window but was detained after a scuffle with police in which a shot was fired. Police said additional arrests were possible.
"The United States congratulates the German government on its success in breaking up the plot by terrorists to attack targets in Germany," a U.S. embassy official in Berlin said.
Germany has not seen a major attack in several years. But concerns about an attack have mounted since two men of Lebanese origin tried to detonate crude bombs hidden in suitcases on trains last year. Prosecutors have said those bombs failed to go off because of a technical flaw.
"We are under threat," Interior Minister Wolfgang Schaeuble told a news conference in Berlin. "We have to remain vigilant."
