Istanbul (CNN) -- Hundreds of people marched in central Istanbul Sunday to protest the Kurdish separatist group PKK killing 13 Turkish soldiers during an ambush Thursday in southeastern province of Diyarbakir.
The demonstration took place along Istiklal street, one of the busiest pedestrian thoroughfares in Istanbul. An emotional crowd waved Turkish flags and carried pictures of the dead soldiers. They sang the Turkish national anthem and chanted slogans such as "Martyrs won't die, country won't be divided" and "Damn PKK."
Riot police took extensive measures along the street and in Taksim Square to prevent the protest from spreading to a nearby Kurdish neighbourhood.
One of the protesters, Servan Oncel, said: "We are one public, one nation and one state. We cannot let anybody to divide our state. This protest meeting does not belong to any political party but belongs to all those who define the unity of our country Turkey."
The Turkish state has been fighting the PKK -- Kurdistan Workers' Party -- since the early 1980s. More than 30,000 people have been killed during the conflict.
Tensions have increased in recent days since the killing of the 13 soldiers. The attack was condemned by U.S. Secretary of State Hillary Clinton during recent her visit to Turkey.
"We stand with Turkey in its fight against the PKK, a designated terrorist organization which has claimed tens of thousands of Turkish lives," Clinton said in a statement. "We support Turkey in its fight against terror and we will continue to work with the Government of Turkey to combat terrorism in all its forms."
The deadly attack on the soldiers has escalated already simmering ethnic tensions in Turkey. A day after the soldiers were killed, famous Kurdish singer Aynur Dogan was forced off the stage during a concert. While singing a song in Kurdish at the Istanbul Jazz Festival, she was booed by angry audience members.
CNN's Ivan Watson contributed to this report.