|Turkish soldiers guard a checkpoint in Diyarbakir in the troubled southeast of the country on June 26, 2016|
The bomb planted by rebels from the outlawed Kurdistan Workers' Party (PKK) exploded on a highway in Mardin province when a vehicle carrying members of the security forces passed by, the state news agency Anadolu reported.
The authorities have launched an operation to hunt down "fleeing terrorists", it added.
Dogan news agency said the victims were soldiers.
The PKK, designated as a terror group by Turkey and its Western allies, has waged a bloody campaign against the Turkish state since it took up arms in 1984 for self-rule in the Kurdish majority southeast.
The Turkish army meanwhile said eight PKK members were "neutralised" on Sunday in ground and air operations in Hakkari province near the Iraqi border, Anadolu reported.
It said 320 PKK militants have been killed in Hakkari since the operations began several weeks ago.
The figures could not be independently verified.