Watched over by hundreds of police officers, some 20,000 people attended the demonstration in Diyarbakir, the largest city in Turkey's mainly Kurdish southeast, organised by the main Kurdish political party, the Democratic Society Party (DTP), under the slogan "Yes to an Honourable Peace".

"There can be no peace without a counterpart," read placards in Turkish and Kurdish, referring to Ankara's refusal to hold a dialogue with the outlawed Kurdistan Workers' Party (PKK) fighting for self-rule in the southeast since 1984.

"I want my language, do not ban my language," read another banner, calling for changes to allow the Kurdish language to be taught as part of the national curriculum.

Many demonstrators held portraits of the PKK's jailed leader Abdullah Ocalan and waved flags in the Kurdish colours of red, green and yellow as songs praising the rebel chief blared out of loudspeakers.

A separate demonstration in Istanbul, organised by trade unions, civic bodies and political parties in support of a democratic and peaceful resolution of the conflict, drew some 5,000 people, media reports said.

The Turkish government announced last month that it was working on a package of reforms to expand the rights of the Kurdish community and secure an end to the 25-year insurgency which has claimed some 45,000 lives.

No details of the package have been released, but Interior Minister Besir Atalay said Monday that the government had no plans for a general amnesty for Kurdish rebels, a key Kurdish demand.

He also ruled out constitutional amendments, shutting the door on calls for Kurds and their language to be recognised under the national charter.

The PKK on Tuesday accused Ankara of failing to take any "concrete or satisfactory" step in its bid to address Kurdish grievances, as it announced that an extension of its unilateral ceasefire until September 22.

"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, said a PKK statement carried by the pro-Kurdish Firat news agency.

"In the meantime, we will watch closely the attitude of the Turkish state ... and make an evaluation," it added.

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

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

Atalay's announcement also drew criticism from the DTP, which campaigns for broader Kurdish rights and risks a possible ban for links with the PKK.

"Without a new constitution, forget about resolving the Kurdish question," party leader Ahmet Turk told the CNN-Turk news channel on Monday.

Opposition parties remain hostile to the plan as well, arguing that broader Kurdish rights would pave the way for Turkey's disintegration.

The army has also 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.

Media reports have said that the government plan may involve restoring the Kurdish names of villages that have been renamed and lifting a ban on using Kurdish in political propaganda.

But sceptics argue that a lasting settlement cannot be achieved if Ankara insists on rejecting dialogue with the PKK and fails to draw up a clear strategy to convince the rebels to lay down arms.