BERLIN, (Reuters) – German security officials are searching for 10 men they believe provided support for a foiled plot to attack U.S. installations in the country, a senior government official said.

On Wednesday, Germany announced that it had arrested three men — two Germans and one Turk — who were on the verge of launching “massive bomb attacks” more deadly than the Madrid and London bombings of recent years.

August Hanning, state secretary in the Interior Ministry and a former head of Germany’s foreign intelligence service (BND), said on Thursday that the three arrested men had backers at home and abroad who were still being tracked. “They are Germans, Turks and there are other nationalities as well,” Hanning told public television station ARD. “This is the network we have identified.”

Germany, which has not suffered a major attack in past years, was shaken by news that the three men whom police took into custody on Tuesday had accumulated vast amounts of bomb-making chemicals and military grade detonators in preparation for an attack.

Officials have said all three of the men had trained in militant camps in Pakistan before forming a domestic cell of the “Islamic Jihad Union” — a little known al Qaeda-affiliated Sunni Muslim group with roots in Uzbekistan.

Bavarian Interior Minister Guenther Beckstein, predicting additional arrests in the coming weeks, said the foiled attack underscored that Germany was now a major target despite its refusal to participate in the 2003 U.S.-led Iraq war. “Germany has become a priority target for Al Qaeda,” he told the online version of German magazine Focus.