"They are in good health," Kurdistan Workers' Party (PKK) spokesman Sozdar Avesta said late on Sunday.

"The PKK is ready to release the three German tourists on condition that Turkey halts its military attacks in the area where they were captured," Avesta told reporters in northern Iraq's Qandil mountain range.

"The area... is a war zone. We demand that there be a ceasefire in the area so we can release them."

The three Germans were seized on Tuesday in Mount Ararat area of Turkey, believed to be the final resting place of the Biblical Noah's Ark. Their current whereabouts are unknown.

Avesta said the release must be facilitated by an international organisation like the Red Cross.

"They were detained by a wing of the PKK which thought they were working against the Kurds in Germany," Avesta said. "Their arrest was a reaction to what Germany is doing. We urge the German government to undertake a new policy towards the Kurds."

On Sunday, the PKK said it would keep the hostages unless Berlin ended a crackdown on PKK militants and their supporters in Germany, which is home to about 2.4 million immigrants from Turkey, including about 600,000 Kurds.

In an interview with Germany's Bild newspaper on Sunday, German Chancellor Angela Merkel issued a personal appeal for the immediate release of the hostages, saying Berlin would not be blackmailed.

Turkish paramilitary troops have launched a sweep to rescue the three men and Mount Ararat has been declared off-limits until further notice.

The PKK, listed as a terrorist organisation by Ankara, the European Union and the United States, has been fighting for self-rule in Turkey's Kurdish-majority east and southeast since 1984. The conflict has claimed more than 37,000 lives.

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

Ankara charges that more than 2,000 Kurdish rebels have found a safe haven in northern Iraq, where they are able to obtain weapons and explosives for attacks inside Turkey.

Turkish troops regularly carry out cross-border raids inside northern Iraq, aided by intelligence from the United States.