Armoured vehicles and 5,000 infantry entered the Kurdish-held region from three different points along the border, while helicopters bombarded Kurdish mountainside hideouts.

Turkish media reported that fighter aircraft had also been involved in attacks on a PKK camp. The private NTV television station said the troops had advanced 10 kilometres from the Turkish border. A contingent of Turkish troops is permanently based in northern Iraq.

PKK peace overtures

The Turkish army has fought a bitter 15-year war with the PKK

The incursion began on Monday, despite new peace overtures from the PKK.

Last week the PKK leader, Abdullah Ocalan, called from his cell on death row for a group of fighters to surrender with their weapons to confirm their commitment to peace. Under a new law they would receive an amnesty.

Earlier in September, Mr Ocalan's brother, Osman, said the PKK would lay down its weapons and start to operate as a political organisation.

But on Tuesday the Turkish army rejected the PKK's offer to seek a negotiated settlement, and said it would continue fighting until the last rebel had been neutralised.

The PKK replied on Wednesday that it would continue to seek peace, but would never surrender.

Guerrillas in retreat

Kurdish guerrillas have said they are retreating from Turkey to northern Iraq in answer to an appeal from Mr Ocalan to abandon their armed struggle and leave the country.

The Turkish army says they are simply moving to Iraqi hideouts to escape the harsh winter in south eastern Turkey.

The German-based Kurdish DEM news agency, DEM, said 15 Turkish soldiers and six guerrillas had died in the latest offensive.

Reports say that pro-Ankara Kurdish militias and Iraqi Kurds opposed to the PKK are backing the Turkish army.

The Turkish army has made frequent incursions into northern Iraq in pursuit of PKK fighters. The area has been outside Baghdad's control since the 1991 Gulf War.