The truce, first announced by the separatist Kurdistan Workers' Party (PKK) in April, had been due to expire on Tuesday.

"Our movement has seen it appropriate to extend the non-action period until the end of" the Eid ul-Fitr festival marking the end of the Muslim holy month of Ramadan on September 22, the PKK said in a statement carried by the Firat news agency.

"In the meantime, we will watch closely the attitude of the Turkish state ... and make an evaluation," it added, accusing Ankara of failing to take any "concrete or satisfactory" step so far in its bid to address Kurdish grievances.

The rebels also urged the government to allow for the announcement of a separate peace plan drawn up by PKK leader Abdullah Ocalan on the Turkish prison island of Imrali where he is serving a life sentence for treason.

Ocalan's lawyers said last month that their client had handed the document to prison authorities and they would make a formal application to be given a copy.

Ankara has never formally recognised PKK's unilateral truces and military operations against the rebels have continued.

The PKK, which took up arms for self-rule in Turkey's Kurdish-majority southeast in 1984, is listed as a terrorist group by Ankara and much of the international community. The conflict has claimed about 44,000 lives.

Last month, the Turkish government announced that it was working on a plan to expand the rights of its Kurdish community and secure an end to the fighting with the PKK.

The government has released no details on the package, but Interior Minister Besir Atalay said Monday that they had no plans for an amnesty for the rebels or constitutional amendments.

Opposition parties remain hostile to the government's plan, arguing that broader rights for the country's Kurds would pave the way for Turkey's disintegration.

The Turkish army meanwhile has warned that the planned reforms must not endanger unity, underlining a constitutional article that describes Turkey as being an indivisible whole with Turkish as its language.