Turkey's Anatolia news agency said that police used water cannon to disperse Kurds in the Istanbul district of Umraniye, while in nearby Kucukcekmece petrol bombs damaged a shopping centre.

The pro-Kurd news agency Firat for its part said that police quashed protests in the cities of Mersin, in the south, Sanliurfa in the southeast -- where vehicles were set on fire -- and Van and Varto in the east.

Another demonstration was planned for Saturday in Diyarbakir, the main city in the Kurdish-majority southeast of the country, the reports said.

Ocalan's lawyers had reported that he had been assaulted by a guard and threatened with death in his island prison of Imrali, in the northwest, where he has been held in solitary confinement since 1999.

Similar reports in the past have stirred anger among Kurds who look on Ocalan, head of the separatist Kurdistan Workers' Party, as a hero.

Arrested in Kenya in February 1999, he was sentenced to death by a Turkish court but the sentence was commuted to life imprisonment in 2002 after Turkey abolished the death penalty.

The PKK is blacklisted as a terrorist organisation by the European Union and the United States as well as by Turkey. Some 44,000 people have died since its conflict with the Turkish state began in 1984.