But the Kurdistan Workers Party (PKK) reserves the right to defend itself if it comes under attack during the ceasefire, said the Firat News Agency, which serves as a mouthpiece for the group.
The ceasefire, first declared on April 14, had been due to expire on Monday.
"The PKK is extending the ceasefire by … one-and-a-half months to July 15 in order to allow for finding a peaceful resolution of the Kurdish problem," the statement said.
"However, the PKK reserves the right to self-defence if it comes under any attack."
The declaration comes after six soldiers were killed and 11 wounded on May 27 in Hakkari province near the Iraqi border, in an explosion blamed on the PKK.
The PKK has waged a 25-year campaign for autonomy in mainly Kurdish southeastern Turkey. The conflict has claimed 40,000 lives, mostly of Kurds. (Writing by Ayla Jean Yackley; editing by Andrew Roche)