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

The discovery comes as the PKK is observing a unilateral ceasefire for the Muslim holy month of Ramadan and with 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.