By Jonny Dymond BBC correspondent in Istanbul

The Kurdish militants declared a truce in 1999

The PKK declared a ceasefire in 1999 following the capture of its leader, Abdullah Ocalan, by the Turkish security forces.

For 15 years the PKK fought the Turkish state in a conflict which claimed more than 30,000 lives.

Its successor has now said it will target Turkish security forces again.

The statement by Kongra-Gel (Kurdistan People's Congress) came through a channel often used by the PKK, the Mesopotamian News Agency.

It said that the ceasefire had become meaningless following what it called annihilation operations carried out against its fighters over the past few months.

Tourists, the statement said, should not choose Turkey and those considering investing should think again.

Calls for peace

It is difficult to know how seriously to take the threat of renewed military action by Kongra-Gel.

For several months, deep divisions have been reported within the organisation, which is thought to have around 5,000 fighters in the far north of Iraq.

It is believed that a sizeable faction wants to renounce the armed struggle once and for all.

There has been an increase recently in activity in the south-east of Turkey which borders northern Iraq.

Some believe that this may have come about as a result of the American military presence in Iraq.