"The PKK fighters shot down a Turkish Cobra helicopter in an area called Cham Chu" on Saturday, Ahmed Danis, spokesman for the rebel group told AFP.

The PKK claim could not be verified independently.

Danis did not provide further details about the reported incident in Cham Chu near the town of Amadiyah, 50 kilometres (30 miles) northeast of Dohuk, capital of the Kurdish province of the same name.

Since Thursday evening's launch of a fresh offensive against PKK rebels in northern Iraq the Turkish military claims it has killed dozens of guerrillas.

The PKK is considered by Ankara, the United States and the European Union to be a terrorist organisation.

Ankara says the PKK uses northern Iraq as a springboard for cross-border attacks as part of its campaign for self-rule in Kurdish-majority southeast Turkey.

The conflict has claimed more than 37,000 lives since it began in 1984.