Qandil Mountains, Iraqi Kurdistan: Turkey has been threatened with a new terrorist campaign of "torture and massacre" at tourist resorts as the holiday season gets under way.

The Kurdistan Workers' Party (PKK), a Kurdish separatist group, has said it plans a wave of violence after the breakdown of a year-long ceasefire.

It will target major Turkish cities, rather than just army patrols and bases in the Kurdish heartlands. These are likely to include towns and cities in western Turkey, including those popular with tourists and businessmen.

A triple bombing struck the resort of Marmaris in 2006, while a year later a suicide bomber targeted a shopping street in the capital, Ankara.

High threat

Some 2.5 million British tourists visit Turkey each year. The Foreign Office advised "against all but essential travel" to the south-east of Turkey due to the "high threat from terrorism".

A spokesman said on Sunday: "Terrorist attacks have also taken place against both government and civilian targets in major cities such as Istanbul, Izmir and Ankara, and tourist resorts on the Mediterranean and Aegean coasts."

Murat Karayilan, the senior commander of the PKK, said he was left with no choice but to act after Turkish bombing raids on his group's bases.

He said the PKK would soon declare "democratic autonomy" in Kurdish regions of south-east Turkey. "If Turkey does not accept this, it is their problem," he said.

The war between the Turkish government and the PKK, which has lasted 26 years and claimed 40,000 lives, has already moved into a new phase after the collapse of a ceasefire.

The prime minister, Recep Erdogan, criticised for making too many concessions, ordered the bombing raids on PKK bases in Iraqi Kurdistan.

The most prominent of these is the remote stronghold in the Qandil Mountains, where The Daily Telegraph was escorted for the interview along back roads hidden from the army drones overhead.

Despite the raids and the weight of one of Nato's largest armies ranged against him, Karayilan said his forces could keep up the struggle for decades more.

Major escalation

"We are deeply rooted in the mountains and hearts of the people of Kurdistan," he said. "We are able to live another 50 years like this."

Erdogan's strategy is to improve strategic ties with its neighbours to the east and squeeze out opposition from the Kurds, who form a significant minority in several countries. He has built bridges with leaders of the autonomous Kurdish region of northern Iraq, which has for years provided a haven for the PKK.

Tens of thousands of Kurds have been arrested under Turkey's anti-terror laws, including 1,600 Kurdish politicians and 4,000 children. Analysts said the PKK threats promised a major escalation of the conflict.

"You will see that Kurds will respond with support. As a result there is going to be a counter wave of repression and it will increase the tension and violence," said Henri Barkey, of the Carnegie Endowment for Peace in Washington.