Turkish riot police fired tear gas and rubber bullets at Kurdish protesters armed with rocks and Molotov cocktails on Monday in a new upsurge of violence that has rattled the fragile peace process.
Two demonstrators have been killed and four soldiers briefly kidnapped by guerrillas in the southeast of the country in the worst unrest since a ceasefire adopted by the outlawed Kurdish rebels nine months ago.
Fierce clashes erupted for a fourth day on Monday in the far southeastern town of Yuksekova, where the trouble first broke out on Friday night over the alleged destruction of the graves of Kurdish fighters.
Police fired tear gas and rubber bullets to disperse about 3,000 Kurds who pelted them with rocks and Molotov cocktails and attacked police security cameras and street lights, an AFP correspondent said.
Turkish Prime Minister Recep Tayyip Erdogan on Sunday accused certain groups of trying to damage the peace process with the Kurdistan Workers' Party (PKK).
"These are actions perpetrated by those who want to hurt the process," Erdogan said. "However, we will continue the process... without falling into this trap."
Interior Minister Muammer Guler on Monday denied the allegations that PKK cemeteries in Yuksevoka had been destroyed, saying they were a "provocation" by unnamed radical groups.
Two protesters were shot dead by police in clashes in Yuksekova on Friday night, setting off weekend protests in several towns including the main southeastern city of Diyarbakir and even Turkey's biggest metropolis Istanbul.
In a statement from his isolated prison cell on the island of Imrali off Istanbul, jailed PKK leader Abdullah Ocalan denounced the deaths.
"These killings are a great provocation against the peace process," said Ocalan.
Four Turkish soldiers in plain clothes were kidnapped on Sunday in a rural area near Diyarbakir by Kurdish rebels who torched their vehicle and whisked them off to an unknown location.
They were freed on Monday after intervention by lawmakers from the pro-Kurdish Peace and Democracy Party (BDP), a local security source said.
"The soldiers were returned to the local authorities and are in good health," the source told AFP.
In the past, Kurdish rebels frequently kidnapped soldiers, workers and local officials as bargaining chips for the release of captured PKK members.
In Diyarbakir, the situation was calm and shops reopened after being closed for two days in protest at police violence, an AFP correspondent said.
On Sunday, police had fired tear gas and water cannon to break up a demonstration in the city by around 5,000 people, some brandishing effigies of Ocalan.
Protesters also hurled explosive devices at a police station in the town of Dogubeyazit near the Iranian border and set fire to a local bank branch in Hakkari near the frontier with Iraq.
Around a dozen people, including four policemen, were injured in Diyarbakir alone, and around at least 22 protesters were arrested, local media reported.
The latest incidents come after months of calm between the Turkish state and the PKK, which declared a truce in March following clandestine negotiations between Ocalan and the country's spy agency.
The process stalled after Kurdish rebels announced in September they were suspending their retreat from Turkish soil, accusing the government of failing to deliver on promised reforms.
The violence erupted after Erdogan's government on Thursday submitted to parliament a so-called "democratisation" package of reforms mainly affecting Kurds.
The reforms include education in Kurdish in private schools, election campaigns in Kurdish and the removal of a ban on the use of the letters Q, W and X, which are used in Kurdish spelling but not in Turkish.
Kurds are also demanding the release of Kurdish prisoners and political activists, the lifting of restrictions on Kurdish-language education in state schools and reducing the 10-percent election threshold required to secure seats in parliament.
The PKK, which is blacklisted as a terrorist organisation by Turkey and much of the international community, launched an insurgency seeking self-rule in the southeast in 1984 that has claimed about 45,000 lives.