Under the banner "hand in hand against terror", more than 20,000 Turkish immigrants and Germans marched through Germany's fourth largest city of Cologne on Sunday to condemn violence by and against Muslims. Amid fears attacks may spread from the Netherlands, Chancellor Gerhard Schroeder in an interview urged Germany's 3.5 million Muslims - 4.2 percent of the total population - to help fight extremism and work harder to integrate.
Religious tensions in the Netherlands erupted with the killing this month of Dutch filmmaker Theo van Gogh. A Dutch-Moroccan man was charged with his murder, sparking a wave of attacks on Muslim and Christian religious targets.
Interviewed by German television on Sunday, Schroeder said: "We've got to say clearly that those who live here and want to integrate have to obey the laws and have to learn our language."
Wolfgang Huber, head of Germany's Protestant church, said the German language should be used in the mosques, telling Focus magazine: "It would be in the interests of the mosques to say, 'We have nothing to hide'."
In the Cologne march, Muslim community leaders joined politicians left and right in condemning violence.
"Open the gates of the mosques and show the good side of Islam," Marielouise Beck, Schroeder's ombudsman for foreigners, told the rally before Turkish, German and European Union flags.
"We're all shocked by the murder of van Gogh. We can't let the violence spill into Germany. Integration is hard work."
A survey for the RTL television network on Sunday found 81 percent of Germans believed foreigners weren't doing enough to integrate themselves, although 52 percent believed foreigners and Germans got along well.
Police and school officials have said Muslims were living in "parallel societies" in many large cities without learning the language or accepting German customs.
"Islam is a religion of peace," Guenther Beckstein, arch conservative interior minister of Bavaria, told the rally. "Terrorists are criminals. Those who burn mosques are not decent Germans. They're criminals."