Turkey's Anatolia news agency said the five were killed in a gun battle in the province of Mardin late on 23 February.
The five were reportedly members of the outlawed Kurdistan Workers Party (PKK).
Turkey blames the PKK for the deaths of more than 30,000 people since the group launched its armed struggle for Kurdish self-rule in southeast Turkey in 1984.
Iraq's Kurdish Region
KURDISH AWAKENING: The ethnic Kurdish region in the northern part of Iraq has struggled in recent years to reestablish its cultural and political identity after decades of oppression under the regime of deposed Iraqi President Saddam Hussein. In December, RFE/RL correspondent Charles Recknagel traveled to this area and filed several reports: