The former member of the Kurdistan Workers Party (PKK), which is classed as a terrorist organisation by Ankara, the European Union and the United States, has been held at Zurich's Kloten airport since his arrest in December 2005 on an international warrant at Turkey's behest.

Swiss authorities approved the man's extradition to Turkey after receiving guarantees that the Swiss ambassador to Ankara could visit the man in a Turkish jail and their conversations would not be monitored.

Rolf Zopfi of the "augenauf" human rights group said these guarantees were insufficient.

The detainee was denied asylum in Switzerland last November but his appeal is still pending, Swiss news agency ATS reported.