"I appeal to the PKK to call a ceasefire... (and) not use weapons unless it is attacked with the aim of being annihilated," he said.

There was no official reaction, but the Turkish army, which has been battling the PKK in southeastern Turkey since 1984, has ignored such ceasefire announcements in the past.

"Such a process ... is very important to build a democratic union between Turks and Kurds," Ocalan said in a statement relayed to AFP by his lawyers, who met him in his cell on the prison island of Imrali, of which he has been the sole inmate since his arrest in 1999.

"With this process, the way to democratic dialogue will also be opened," Ocalan said.

Ocalan, despite serving a life sentence for separatism and treason, is believed to retain significant influence over the PKK, which has been plagued by internal fighting since his arrest.

The rebel group, classed as a terror organisation by Turkey, the European Union and the United States, had called a truce immediately after Ocalan's 1999 arrest in Kenya, but took up arms again in June 2004 and has significantly increased its attacks since, notably this year.

It was the longest lasting of four PKK ceasefires over the years, all of which were rejected by the army, which wants the rebels to lay down their arms and surrender or face being hunted down to the last militant.

More than 37,000 people have died in Kurdish-populated southeast Turkey since the PKK uprising began in 1984.

Ocalan said through his lawyers, who regularly visit him on Imrali, that the latest truce offer should not be interpreted by Ankara as a sign of PKK "weakness," but as an occasion to achieve reconciliation between Turks and Kurds.

"At the point we have come to, the bloodshed should stop and peace should be given a chance," he said, adding that this "could be the last chance."

Since the beginning of this year, when PKK violence resumed with a vengeance, 78 members of the security forces and 110 PKK members have been killed, according to an AFP count.

Another extremist Kurdish group calling itself the Kurdistan Freedom Falcons (TAK) has emerged over the past couple of years and claimed responsibility for a series of deadly bomb attacks in Turkey's urban centers and tourist resorts.

The PKK says TAK is a breakaway group over which it has no control, while the army maintains that it is simply a front for the PKK to attack soft civilian targets without tarnishing its "freedom fighter" image.

Hundreds of armed PKK fighters are entrenched in the rugged mountains of east and southeast Turkey, while an estimated 5,000 more are based in Kurdish-ruled northern Iraq, where many of them fled after the 1999 ceasefire.

They have been infiltrating Turkey in growing numbers since the truce was called off and Ankara has been actively trying to get Washington and Baghdad to intervene against them militarily, so far to no avail.

Turkey often organized military incursions into northern Iraq before the allied invasion in 2003 and recently threatened to do so again, but was discouraged by the United States.

In hopes of reinforcing its bid to join the European Union, Turkey has recently undertaken a series of reforms, such as allowing Kurdish-language private schools and radio and television broadcasts.

But many Kurds, who number an estimated 10 to 15 million of Turkey's 73 million population, say these are cosmetic measures and more should be done, including giving Kurdish official language status along with Turkish.