Observers from the pan-European rights watchdog rejected, however, suggestions by Ocalan's relatives that he had been poisoned, in a report after visiting him on a Turkish prison-island in the Sea of Marmara in May 2007.

The 59-year-old leader of the separatist Kurdistan Workers Party (PKK) has been serving a life sentence for treason and separatism as the sole inmate on the island of Imrali since his capture and conviction in 1999.

His supporters claimed last year that he was being progressively poisoned in prison, citing test results indicating high levels of toxic metals, including chromium and strontium, in his body.

In its report, the Council of Europe Committee for the Prevention of Torture (CPT) confirmed high levels of heavy metals were present in Ocalan's hair and chest-hair, but should not be "interpreted as dangerous for (his) health."

"They are very probably linked to the individual's environmental conditions" near the sea, and to his food habits, said the report, citing findings by CPT experts in Geneva.

But the experts warned Ocalan's mental health "has noticeably deteriorated" since the committee's previous visits in 2001 and 2003, due to "chronic stress and prolonged social and emotional isolation" and "a feeling of abandonment."

They urged Turkey to "completely revise Abdullah Ocalan's situation with the aim of integrating him into a place where contacts are possible with other prisoners and which would allow him a greater range of activities."

The experts said he should be allowed to watch television, phone his relatives and see his lawyers alone, and receive more regular visits.

Ankara flatly rejected the Council of Europe's demands in a written response to the report.

"The convict is the leader of a terrorist organisation that has conducted violent acts causing the death of 25,000 people," the government wrote, arguing that the risk of Ocalan escaping was too great to consider a transfer.

Ocalan's original death sentence was later commuted to life in prison as Turkey abolished capital punishment as part of EU-sought reforms.

Police and protesters clashed in southeastern Turkey early this month after the ninth anniversary of the rebel leader's capture, claiming a teenager's life, while some 10,000 Kurds protested in Strasbourg to demand his release.

The Kurdish conflict in Turkey has claimed more than 37,000 lives since 1984 when the PKK, listed as a terrorist group by Turkey and much of the international community, took up arms for self-rule in the southeast.

Since December 16, Turkish warplanes have carried out five bombing raids on PKK positions in northern Iraq, where the group takes refuge.