The Turkish Foreign Ministry said Italy had not acted in accordance with the law.

Tom Butler reports: Turkey said it would find Mr Ocolan

The new Turkish Prime Minister, Bulent Ecevit, said his government was determined to pursue Mr Ocalan and would not allow him to escape justice.

Mr Ocalan, the leader of the Kurdistan Workers' Party (PKK), arrived in Italy in November, seeking political asylum. He was then arrested on a German warrant.

Ankara wants Mr Ocalan to face trial on charges of treason in Turkey. But Italy rejected Ankara's request for Mr Ocalan's extradition on the grounds that he could face the death penalty if he was handed over.

A statement from the Italian Prime Minister, Massimo D'Alema, said that what he called a difficult and complex case had been resolved in full accordance with national and international law.

Destination unknown

The Ocalan case strained Turkey's ties to Italy

There was speculation that Mr Ocalan had gone to Moscow, but this has been denied by Russian officials.

Meanwhile, Turkish security officials said the Kurdish leader may have gone to South Africa or another African country, according to the Turkish news agency, Anatolia.

A report on London-based Kurdish Med TV said Mr Ocalan had asked his lawyers in Italy to continue pursuing his asylum application.

'Aggressive diplomacy'

The BBC Ankara correspondent says that wherever the Kurdish rebel leader does surface, he will remain the target of aggressive Turkish diplomacy.

News of his departure from Italy follows several weeks of negotiations between Italy and several European and African countries with a view to finding a new home for Mr Ocalan.

The Kurdish leader was freed last month by a Rome appeals court. Despite seeking political asylum in Italy, Prime Minister D'Alema had publicly branded him a terrorist and favoured an international trial.