"Thousands of people will die in Turkey, civilians as well as soldiers," Osman Ocalan told AFP in his home in Koya across the border in Iraqi Kurdistan.

"The PKK has more than 7,000 fighters," said the PKK leader's brother who spent 18 years fighting Turkish troops before abandoning the armed struggle in 2004.

"I am sure that if Apo (uncle in Kurmanci Kurdish -- Ocalan's nickname) dies, 5,000 of them will volunteer for suicide operations in the heart of Turkish cities."

Osman Ocalan, whose family has the right to make weekly half-hour visits to the PKK leader on the prison island of Imrali, south of Istanbul, where he is the sole inmate, said that his brother's health was "bad".

"He has a great deal of difficulty breathing. His lungs are damaged. We are very worried.

"The PKK has been asking for months that a team of doctors be allowed to examine him but Ankara refuses. Is that because they've something to hide? Apo is the PKK and the PKK is Apo. We must continue the fight for his release."

Ocalan, who was detained in Kenya in 1999 after being forced out of his longtime base in Syria, is serving a life sentence for separatism and treason.

The PKK launched its armed struggle for Kurdish self-rule in southeastern Turkey in 1984. More than 37,000 people have died.

The group has stepped up its attacks in recent months, drawing Turkish threats of military action against PKK rear-bases in northern Iraq and of restrictions on the booming trade across the border.