Sixteen organizations, including the Central Council of Muslims in Germany, issued a joint statement saying they were "deeply shocked and horrified."

"Islam offers no justification for such acts," added the groups.

They said Muslims could have been victims in more than one sense if the plot to blow up trains outside the cities of Hamm and Koblenz on July 31 had succeeded. Homemade bombs planted on the trains in trolley suitcases failed to explode, averting an almost certain bloodbath.

"If such an attack succeeds, we are potential victims of such attacks, along with all other citizens. But we will also be branded 'co-accused'," the groups said.

Their statement follows a call by Interior Minister Wolfgang Schäuble earlier this week on Muslims to condemn the plot, which he has described as a terrorist attempt to kill countless people.

Two young Lebanese men who have been living in Germany have been arrested in connection with the plot. One of them turned himself in to police in Lebanon, where officials on Friday said he had made a confession.

Police are holding two more people, one in southern Germany and one in Lebanon, for questioning. Media reports have suggested that the attack may have been planned in retaliation for Israel's offensive on Lebanon.

According to a report in the Frankfurter Rundschau daily, the Central Council of Muslims is considering new ways to work with security officials. The group's president, Aiman Mazyek, told the paper that a "kind of pilot project" had been agreed upon with officials in the state of North Rhine-Westphalia that aims at improving relations between mosques and the police.

Demand to go further

But conservative politician Edmund Stoiber, head of the Bavarian-based Christian Social Union, said "a common condemnation of terror is an overdue first step, but it's not enough." He told the Bild am Sonntag newspaper that Muslims in German needed to become active in trying to prevent terrorist attacks.

He called on Muslim communities to reject extremists in their ranks and alert security officials to them. He added during Friday prayers imams should not denounce western values as morally inferior, thereby radicalizing young Muslims.

Germany is home to about 3.4 million Muslims, of whom two-thirds are of Turkish origin.