The blast struck a section of the pipeline in the southeastern region of Mardin near the village of Midyat, sparking a blaze that firefighters were still fighting to get under control, local security sources said.

The authorities suspect the PKK carried out the attack, but the group has not claimed responsibility, although they have attacked the pipeline in the region several times, including last month.

The 970-kilometre (600-mile) pipeline carries crude oil from Kirkuk in northern Iraq to Ceyhan, where it is loaded onto tankers.

The PKK, listed as a terrorist group by Turkey and much of the international community, took up arms for self-rule in the Kurdish-majority southeast in 1984, sparking a conflict that has claimed around 45,000 lives.

It has significantly stepped up attacks since its jailed leader Abdullah Ocalan declared in May that he was abandoning efforts to seek dialogue with Ankara.