In a speech marking the anniversary, Merkel cited a government-commissioned report that found economic discrepancies between the eastern and western parts of Germany and which said people in the east feel like second-class citizens.

But she said this was no justification for verbal attacks on foreigners under the guise of free speech, and that such attacks threatened democracy in Germany. Shortly after she spoke, about 600 people took part in a far-right rally in Berlin, with some carrying German flags and waving anti-Islam placards.

Merkel did not mention the anti-migrant AfD by name but it has stronger support in eastern parts of Germany and made big gains in elections in two eastern regions last month.

"It should never be the case that disappointment with politics, however significant, be accepted as a legitimate reason to marginalize, threaten or attack others because of their skin color, religion, sex, or sexual orientation," Merkel said in the northern city of Kiel.

"The values of our constitution must guide each and every debate in our country," she said. "In concrete terms, this means, 'Yes' to open debate, 'Yes' to tough demands from politics, 'No' to intolerance, 'No' to marginalization, 'No' to hate and anti-Semitism, 'No' to living at the expense of the weak and minorities."

REUTERS