"We have started constructing new accommodation on Imrali (the northwest island where Ocalan is imprisoned) and I think it will be ready in May, after which we will decide whether to send prisoners there or not," Justice Minister Mehmet Ali Sahin told NTV news channel.

"We expect to increase the number of detainees to this prison but a final decision has not yet been taken," he added.

Last month Sahin said "five or six prisoners" could be transfered to the island.

Ocalan, 59, 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.

In March the Council of Europe's anti-torture committee (CPT) urged Turkey to end his solitary confinement, stressing the threat to his mental health after visiting him on the prison-island in the Sea of Marmara in May 2007.

Experts from the pan-European rights watchdog warned Ocalan's mental health had 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 allow Ocalan to have contact with other prisoners and allow him a greater range of activities such as watching television, phoning his relatives and receiving more visitors.

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.