The explosives, along with 15 rocket-launchers, had come across the border from northern Iraq, according to the office of the governor of Sirnak. No date for the operation was given.

Both southeast Turkey and northern Iraq have large Kurdish populations.

The explosive, C4, also known as Semtex, has been used by the outlawed Kurdistan Workers' Party (PKK) and the radical Kurdish group the Kurdistan Freedom Falcons (TAK).

The TAK has claimed responsibility for a number of attacks in tourist centres in recent days which left three dead and about 50 injured, among them 10 British holiday-makers.

The Turkish authorities regard the TAK and PKK as largely interchangeable, believing that the PKK uses the name of the TAK when it conducts operations aimed at civilians and likely to anger international public opinion.

Ankara, the European Union and the United States all classify the PKK as a terrorist organisation. Several thousand of its members are believed to have sought refuge in northern Iraq.

More than 37,000 lives have been lost in the Kurdish insurrection which began in 1984 with Kurdish demands for independence for the southeastern and heavily Kurdish Anatolia region.