The zones -- where civilians are barred -- cover uninhabited mountainous regions in the provinces of Siirt, Sirnak and Hakkari, close to the border with Iraq, where the rebels have bases.

They were established on June 9 initially for a three-month period.

In Friday's statement, the general staff said that the zones would also remain in force from September 10 until December 10.

Turkey says thousands of rebels from the outlawed Kurdistan Workers' Party (PKK) use bases in the Kurdish-held autonomous north of Iraq as a springboard for attacks on Turkish targets across the border.

The rebels have significantly stepped up their attacks this year. In response, the Turkish army has reinforced its presence in the southeast and along the Iraqi border.

More than 37,000 people have died since 1984 when the PKK, listed as a terrorist group by Ankara and much of the international community, took up arms for self-rule in Turkey's mainly Kurdish east and southeast.

Turkey has long pressed the United States and Iraq to wipe out the PKK's presence in northern Iraq and has threatened to launch a cross-border operation if they fail to do so, a move opposed by both the United States and Iraq.