"We demand the immediate and unconditional release of the three kidnapped men," a foreign ministry spokesman told reporters, adding that Berlin was in constant contact with Turkish authorities.

"We are doing all that we can to resolve the matter in the best way," he said.

A security source told AFP there had been no direct contact with the kidnappers from the PKK, which has waged a bloody struggle for self-rule in Turkey's Kurdish-populated southeast since 1984.

On Thursday, the group confirmed that it had seized Tuesday three Germans who were on a climbing trip on Mount Ararat and set political demands for their release.

"The German tourists will not be released unless the German state announces that it has given up its hostile policies against the Kurdish people and the PKK," the statement said.

Berlin rejected the demands.

"The federal republic does not respond to blackmail," said Foreign Minister Frank-Walter Steinmeier.

Interior Minister Wolfgang Schaeuble said a team from the German police had been sent to Turkey to assist local authorities handle the crisis.

Turkish paramilitary troops have launched a sweep to try to rescue the hostages and Agri governor Mehmet Cetin told the Anatolia news agency Thursday that Mount Ararat had been declared off-limits until further notice.

The PKK is listed as a terrorist group by Ankara, the European Union and the United States, and has been banned in Germany for 15 years.

The group has in the past kidnapped people, among them soldiers, police officers and tourists, but this is not a tactic it frequently employs.