"We have put everything on the line to maintain the ceasefire... despite attacks, oppression and acts of elimination against us. In the face of these developments, the ceasefire has rapidly become impossible to implement," Cemil Bayik was quoted by the pro-Kurdish Firat news agency as saying on its website.

"Everyone should know that we will reconsider our decision (for a ceasefire)" if the Turkish government does not cease its attacks against PKK rebels, improve the treatment of the Kurdish community and pave the way for dialogue, he added.

The PKK, which has been fighting the Turkish army since 1984, ordered a unilateral ceasefire from October 1, saying it hoped this would pave the way for a dialogue to resolve the conflict.

The truce, like the previous ones called by the PKK, was quickly rejected by Turkey but fighting has decreased markedly since then.

Ankara's actions since the declaration of the ceasefire "have long ago given us the right to use our legitimate right of defence and retaliation", Bayik said.

"But there is a limit to this. If that limit is exceeded, it will not be accepted and will be met with great resistance," he added.

Turkey says thousands of PKK rebels are sheltering in neighbouring northern Iraq which the militants use as a springboard for attacks on Turkish targets across the border.

Ankara has long pressed the United States and Iraq to stamp out the PKK presence in Kurdish-populated northern Iraq, where it says the rebels enjoy unrestricted movement and easily obtain weapons and explosives.

But the United States and Baghdad have been reluctant to crack down on the rebels, saying they are swamped by violence in other parts of the country.

More than 37,000 people have been killed since the PKK, classified as a terror organisation by Turkey, the United States and the European Union, took up arms for self-rule in the country's mainly Kurdish southeast.