Three people, including a teenager, were killed in a gunbattle that erupted overnight in the Silopi district of Sirnak province, near the border with Iraq and Syria, the Sirnak governor's office said in a statement.
Supporters of the Kurdistan Workers' Party (PKK) attacked security forces with homemade explosives, rocket launchers and long-range rifles, set up barricades and placed mines.
Three Kurds, one of them a 17-year-old, died of gunshot wounds in hospital, Silopi mayor Seyfettin Aydemir told AFP.
The shootout started after police came under fire in Silopi as they were sealing trenches which had been dug by the PKK youth wing to prevent them from entering neighbourhoods and detaining suspected militants.
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Clashes continued in and around Silopi throughout the day, with television footage showing columns of smoke billowing from the buildings while gunfire and loud booms were heard in the background.
Ferhat Encu, a lawmaker from pro-Kurdish Peoples' Democratic Party (HDP), claimed on Twitter that police had torched six houses and fired on an ambulance carrying wounded civilians to hospital.
In the eastern Agri province, one Turkish soldier and an Iranian bus company employee were killed in an attack by PKK militants, security sources told AFP.
Three Iranians were also injured in the attack, sources said.
The Turkish army said in a statement that the soldier was killed in an "atrocious" and "heinous" attack by the "separatist terror organisation", its customary phrase for the PKK.
After a series of attacks in Turkey, Ankara has launched a two-pronged offensive to bomb Islamic State (IS) militants in Syria and PKK rebels in northern Iraq and southeast Turkey.