About 3,000 people attended a meeting in Diyarbakir, the largest city of Turkey's mainly Kurdish southeast, to denounce Ocalan's capture on February 15, 1999 and his current solitary confinement in a high-security jail.

The protest turned ugly when police stopped the crowd from marching through the city and came under a hail of stones and sticks, an AFP reporter said.

Some protesters barricaded streets and burned tyres, shouting "Long live chairman Apo," using Ocalan's nickname.

Security forces responded with tear gas and water cannon, detaining about 30 people.

Similar unrest broke in downtown Istanbul where demonstrators blocked a busy street following a gathering to denounce Ocalan's capture, prompting police to use tear gas, an AFP photographer said.

Violent Kurdish demonstrations are frequent on the anniversary of Ocalan's capture.

The 60-year-old founder of the separatist Kurdistan Workers' Party (PKK), was captured in Nairobi, Kenya after he was forced to leave the Greek embassy, where he had taken refuge while on the run after leaving his long-time safe haven in Syria the previous year.

A Turkish court sentenced him to death for treason several months later, but the sentence was commuted to life in 2002 after Ankara abolished capital punishment as part of reforms to align with European Union norms.

For many Kurds, however, he remains a national hero and his conditions in jail are closely followed.

The PKK, listed as a terrorist group by Turkey and much of the international community, took up arms against Ankara in 1984, sparking a conflict that has claimed some 45,000 lives.