The bomb, which consisted of 20 kilos of explosives and two propane tanks rigged to a timer, was discovered along the pipeline linking oil fields in Batman province to Diyarbakir, said the region's governor Mustafa Toprak.

The PKK Kurdish rebel group claimed responsibility for an August 10 blast that hit another pipeline linking Kirkuk in northern Iraq to Turkey's Mediterranean port of Ceyhan and killed two people.

Turkish security forces also arrested late Saturday three suspected members of the PKK Kurdish rebel group after finding 65 kilos (143 pounds) of explosives stashed in their car, security officials said.

The explosives were found in the fuel tank of the car, which was intercepted in Diyarbakir, the main city in the Kurdish-majority southeast of Turkey.

The discoveries come as the PKK is supposed to be observing a unilateral ceasefire it called for a period that covers the Muslim holy month of Ramadan and a referendum on constitutional changes to be held on September 12.

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.