The Baku-Tbilisi-Ceyhan (BTC) pipeline at Refahiye in eastern Turkey has been on fire since the blast on Tuesday night and is expected to be closed for 15 days.

The separatist Kurdistan Workers' Party (PKK) said the explosion was "an act of sabotage" by its militants and more details would be revealed later, according to a report on the website of the Firat news agency which is close to the rebels.

The PKK, listed as a terrorist group by Turkey and much of the international community, has sabotaged gas and oil pipelines in the past as part of its armed campaign for self-rule in the mainly Kurdish southeast.

The blast occurred Tuesday night in a pump at a section of the pipeline near Refahiye, in Erzincan province.

An official from Turkey's state-run oil and gas company, BOTAS, told Anatolia news agency Thursday that no trace of a sabotage had been found but a definite conclusion could be made only after the fire at the pipeline was extinguished.

Refahiye's sub-governor had earlier ruled out sabotage, saying a fault had been detected before the blast. The pipeline is expected to remain shut for about 15 days for repair works.

The suspension caused fresh jitters at the world oil markets Thursday, pushing up prices back towards 120 dollars.

Inaugurated in 2006, the 1,774-kilometre (1,109-mile) BTC pipeline is the world's second longest.

It carries Azeri oil from the Caspian Sea fields, the world's third largest reserve, to Turkey's Mediterranean port of Ceyhan, from where tankers transport the crude to Western markets.

It was pumping about 1.2 million barrels of oil per day before the blast.

Analysts suggested the shutdown could last longer than Turkish officials estimate and British energy giant BP said it was looking at alternative means of delivering supplies to Western clients.

The PKK took up arms for Kurdish self-rule in Turkey's southeast in 1984, sparking a conflict that has claimed more than 37,000 lives.

Last week, the Turkish authorities blamed the group for two bomb blasts in in Istanbul on July 27, which killed 17 people, including five children, and wounded more than 150.

Officials believe the attacks were carried out in retaliation for an intensified military crackdown against the PKK inside Turkey and in neighbouring northern Iraq, where the rebels take refuge.

Turkish warplanes have staged air raids against PKK bases in northern Iraq since December, helped by US intelligence on rebel movements in the region.

In February, the army also conducted a week-long ground incursion in northern Iraq, killing at least 240 PKK militants and destroying dozens of hideouts, training camps and ammunition depots.

On Wednesday night, the rebels fired rockets at a police station in the eastern town of Malazgirt, killing a policeman and leaving three others injured.