Turkey's state run Anadolu Agency says Monday's blast targeted soldiers and village guards travelling on a highway in Mardin province, near the Syrian border.
Suspected Kurdistan Workers Party (PKK) militants detonated an explosive device that had been planted in the road, security sources said.
There were no immediate claims of responsibility for the attack on a busy route between the towns of Derik and Kiziltepe.
Fighting between the Kurdistan Workers' Party, or PKK and Turkey's security forces resumed last year after a fragile peace process collapsed. Since then, more than 600 Turkish security personnel and thousands of PKK militants have been killed, according to Anadolu.
Tens of thousands of people have died overall since the PKK - considered a terror organisation by Turkey and its allies - took up arms in 1984.
