Turkish President Abdullah Gul has been forced to delay a speech at Berlin's Humboldt University after a bomb threat.
The German police evacuated the hall after the threat late on Monday, but no explosive device was found, Deutsche Welle reported.
At the start of his speech, a Kurdish radio station urged viewers all day to disrupt his visit to the university on Unter den Linden avenue.
About 50 demonstrators from Kurdish rights groups also held a demonstration near the university.
Gul eventually gave an abridged version of his speech two hours later to a limited audience.
Earlier on Monday, Gul met with his German counterpart Christian Wulff and said Turkey will not be satisfied with anything less than full membership in the European Union.
Turkish-German relations have been marred by Germany's refusal, together with France, to allow Turkey's full EU membership. Ankara began accession negotiations in October 2005.
Gul's visit comes on the 50th anniversary of an agreement that opened the way for mass immigration of Turkish workers to Germany.
He arrived in Germany on Sunday and will leave the country on Wednesday after talks with Chancellor Angela Merkel.