The Turkish authorities confirmed a helicopter had crashed returning from an operation against PKK rebels but did not say why.

The attack near the city of Hakkari came after the PKK leader Abdullah Ocalan, under house arrest in Italy and facing possible extradition, issued a threat that his guerrillas could escalate their 14-year conflict with Turkey.

Chris Morris in Ankara: PKK's options

Mr Ocalan remains at the centre of a diplomatic storm as Turkey continues to demand his extradition from Itlay.

He has been charged with murder and terrorist offences linked to the deaths of 30,000 people during the conflict.

Speaking to Kurdish satellite television channel Med TV on Friday, Mr Ocalan said: "If we were to show our real armed power, the results would be much worse".

Turkish diplomats flew to Italy on Saturday to request Mr Ocalan's extradition.

Mr Ocalan, who has been held in Rome for two weeks, is also wanted in Germany on charges of incitement to murder.

German authorities have not requested his extradition amid fears of increasing tensions between the country's large Turkish and Kurdish populations.

Italy has said it will not extradite Mr Ocalan to Turkey because it has the death penalty.