Police clashed with stone-throwing demonstrators across the country's predominantly Kurdish southeast Sunday during protests marking the 10th anniversary of a separatist rebel leader's capture, state-run media reported. Police fired water cannons and tear gas to break up the protests about the continued imprisonment of Abdullah Ocalan, the leader of the Kurdistan Workers' Party, or PKK, the Anatolia news agency reported. Fighting broke out in Istanbul and across the southeast, including the region's largest city of Diyarbakir, where a group of 1,500 people on an illegal march defied police warnings to disperse. Police said they detained some 50 protesters and that around 20 people, including police officers, were injured. The PKK has fought for autonomy in the region since 1984 and thousands of people have been killed. The United States and the European Union regard the PKK as a terrorist group.