The six-member group from the Council of Europe's Committee for the Prevention of Torture (CPT) spent several hours on the prison island of Imrali in northwestern Turkey on Tuesday, interviewing Ocalan and the five other inmates there, according to the reports.

The delegation was to prepare a report on its findings.

The 61-year-old Ocalan has been serving a life sentence for treason since 1999 for the 25-year bloody armed campaign his outlawed Kurdistan Workers' Party (PKK) has been waging for Kurdish self-rule.

He was the sole inmate on the island until November last year when the Turkish justice ministry transferred five inmates to the island and moved Ocalan to a new cell to allow contact between the prisoners.

The new arrangement came after the CPT criticized Ankara for violating Ocalan's human rights through solitary confinement, but it soon drew complaints from the rebel leader.

Ocalan told his lawyers that his new cell was small and that his prison conditions were turning him into "a man who is half living and half dead", triggering Kurdish street protests across Turkey.

Turkey has rejected Ocalan's claims, saying that his conditions conform to international standards.