By Seyhmus Cakan
DIYARBAKIR, Turkey, Feb 15 (Reuters) - Thousands of Kurds rallied in towns across Turkey's mainly Kurdish southeast on Sunday and some clashed with riot police in calling for the release of Kurdish rebel leader Abdullah Ocalan on the 16th anniversary of his capture.
Ocalan, leader of the separatist Kurdistan Workers Party(PKK), is viewed by nationalist Turks as responsible for the deaths of tens of thousands of people in the group's 30-year armed struggle with the Turkish army.
But for many of Turkey's estimated 15 million Kurds, the 65-year-old represents their bitter struggle for greater cultural and political rights.
Ocalan may call an end to the PKK's armed struggle by March, some people close to the process say. But some also say that unrest in the southeast suggests the PKK is flexing its muscles as it looks to stamp its authority on the mainly Kurdish region.
Four months after deadly riots provoked by Kurdish anger at Ankara's reluctance to help defend their kin in Syria, fresh unrest broke out in the town of Cizre near the Syrian and Iraqi frontiers between security forces, PKK supporters and Kurdish Islamists. At least six people were killed during the riots last month.
Those involved in talks remain tight-lipped on details, fearful of undermining prospects for a final deal. Kurds have been pushing for Ocalan's release, an amnesty for fighters and steps towards autonomy.
"The Kurdistan freedom struggle will from now on aim for the freedom of leader Apo (Abdullah Ocalan). We will step up the struggle for a free Kurdistan," PKK-linked political umbrella group KCK said in a statement on Sunday.
Ankara's hopes of a complete end to the PKK as an armed group have been frustrated by the role it has carved out for itself fighting in Syria and Iraq against Islamic State.
On Saturday night and Sunday, demonstrators and police fought in streets in Sirnak and Diyarbakir, the main city in Turkey's predominantly Kurdish southeast.
Shops kept their shutters lowered in a sign of protest and thousands took to the streets holding up recent photographs of their jailed leader. Police detained 17 protesters in Sirnak.
"Long live leader Ocalan," protesters chanted.
The Turkish government launched talks with Ocalan in 2012. The PKK, which is designated as a terrorist group by Turkey, the United States and the European Union, subsequently declared a ceasefire and began withdrawing from Turkey to camps in northern Iraq where they are based.
Turkish Prime Minister Ahmet Davutoglu said on Saturday the peace process had reached a critical stage and that he expected "a beautiful spring" if the arms were silenced.
"Arms should totally leave Turkey's agenda. Then, beautiful steps will be taken and the country will go through an atmosphere of spring," he said. (Writing by Ece Toksabay; Editing by Stephen Powell)