Police detained at least 25 people in Istanbul early Monday during citywide protests against operations targeting the PKK terrorist group, Turkish security sources said.Protesters, who gathered in different districts of Istanbul, attacked security personnel with Molotov cocktails and stones. Some municipality buses were also reportedly burnt.Police dispersed the protesters with water cannons and teargas.In a separate incident on Sunday, gunmen shot dead a teenager during a protest in Turkey's southern Mersin province, security sources said.According to the sources, supporters of PKK held an "unauthorized demonstration", blocked the road and clashed with police in Mersin's Akdeniz town.Police have launched an operation to nab the perpetrators.The PKK -- considered a terrorist organization also by the U.S. and the EU -- resumed its terrorist campaign in late July. Since then, more than 200 members of the security forces have been martyred and over 1,700 PKK terrorists killed.