"We have started a new building at Imrali," the island prison where Ocalan has been serving a life sentence for treason and separatism as the sole inmate since his capture and conviction in 1999, Justice Minister Mehmet Ali Sahin told journalists.

"We could transfer five or six detainees" to join the 59-year-old head of the separatist Kurdistan Workers Party (PKK), television channels quoted Sahin as saying, adding, "It is being studied."

The Council of Europe's Committee for the Prevention of Torture (CPT) called on Turkey in March to end Ocalan's isolation, after representatives who visited him in May 2007 expressed alarm at the deterioration in his mental health.

The experts said Ocalan was suffering from "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 to the prison in the Sea of Marmara.

But 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 was arrested in Kenya by Turkish agents with the aid of US intelligence in February 1999 and condemned to death after a trial in Turkey.

The sentence was later commuted to life in prison as Ankara abolished capital punishment as part of reforms sought by the European Union, which Turkey hopes to join.

Contacted by AFP, one of Ocalan's lawyers, Hatice Korkut, said she was unconvinced by the minister's statement, as the government could have easily acted earlier to improve her client's conditions, notably by giving him access to newspapers and making visits easier.

But she added that if the government's plans were implemented it would be "a good thing" and could calm Turkey's Kurdish minority, who frequently stage sometimes violent demonstrations in support of Ocalan.

The PKK, considered a terrorist organization by Ankara and much of the international community, took up arms for self-rule in Turkey's mainly Kurdish southeast 24 years ago, sparking a conflict that has claimed some 44,000 lives.