The protesters had gathered in Istanbul's Istiklal Street on Sunday in solidarity with residents of the southeast town of Cizre, where tens of thousands of people had taken to the streets that day to bury 16 people killed in earlier clashes during a week-long curfew, Reuters reported.
Weeks of fresh unrest had hit the mainly Kurdish southeast, where the outlawed PKK has been fighting a decades-long separatist insurgency for greater Kurdish autonomy.
Turkey has staged airstrikes and ground operations against the PKK in its strongholds of southeastern Turkey and northern Iraq in a bid to inflict a mortal blow to its capacities.
But the PKK has hit back, killing dozens of Turkish police and soldiers in almost daily attacks, with the bloodier attacks marking a new intensification of the conflict. More than 100 Turkish security personnel have been killed in attacks mainly in Turkey’s southeastern provinces.
The group is designated a terrorist organization by Turkey, the European Union and the United States. Turkish President Tayyip Erdogan has promised the fight against the insurgents will go on until "not one terrorist is left".
The conflict has flared up as Turkey prepares for a snap parliamentary election on November 1 after a June vote was inconclusive.