Kurdish separatist fighters have declared a unilateral ceasefire against Turkish military forces for the Muslim holy month of Ramadan.

Bouzan Teken, a spokesman for the Kurdistan Workers Party (PKK), said the ceasefire will run until September 20 and could last longer if Turkey satisfies certain conditions.

He told reporters from a PKK base in northern Iraq on Friday that his group will "cease all their military operations inside Turkey" but will defend themselves if attacked.

"We believe that a ceasefire at this time might have positive results towards developing a political and peaceful solution," Teken said.

The PKK said a lasting ceasefire could be possible if Turkey halts its military operations, releases some 1,700 detained Kurdish politicians and starts peace negotiations with the separatist group.

Demands 'unacceptable'

The PKK, labelled a "terrorist" organisation by Turkey and the US, stages hit-and-run attacks against Turkish targets in its quest for Kurdish autonomy, particularly in Turkey's southeast.

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The Turkish government has in the past rejected the PKK's unilateral ceasefire declarations, saying a ceasefire requires two legal parties in conflict. 

But Abdullah Gul, Turkey's president, said he hoped the month of Ramadan would give the PKK a chance to change its ways, adding that the country would never give in to "terror".

However, Haldun Solmazturk, a retired brigadier-general formerly with the Turkish military, told Al Jazeera that the ceasefire is part of the PKK's broader strategy.

"They aim to force the Turkish government to accept some conditions," he said.

But the PKK's demands are all completely unacceptable to the Turkish government, Solmazturk said.

The detainees "are not considered politicians [by Turkey], they are accused of supporting a terrorist organisation," he said.

'Self-defence'

Friday's ceasefire announcement came just days after Turkey accused PKK fighters of blowing up a pipeline in southeastern Turkey carrying Iraqi oil.

Asked about PKK involvement in the pipeline attack, Teken said: "Yes, our troops have done that. It's part of our self-defence. Oil is not just related to the economy but has been turned into a weapon against us."

Rebel attacks have intensified in the country since June, after the PKK called-off a 14-month ceasefire, saying the government rejected their calls for dialogue.

Teken said 71 PKK fighters had been killed in military operations between June 1 and August 9. On its website, the Turkish military said at least 46 soldiers have died since June.

Sunday will mark the 26th anniversary of the conflict that has claimed tens of thousands of lives since 1984.