The action against the Democratic Society Party (DTP) by Supreme Court prosecutors came amid heightened tensions with Iraq caused by Turkey's threat to launch cross border attacks on Kurdish guerrilla bases.

Prosecutors have asked the Constitutional Court to ban the DTP, according to court documents.

"The party in question has become a base for activities which aim at the independence of the state and its indivisible unity," through its links to the Kurdistan Workers' Party (PKK), said chief prosecutor Abdurrahman Yalcinkaya in a statement to the court.

The DTP was founded in 2005 after another pro-Kurd party was ordered to disband because of alleged links to the outlawed PKK.

DTP deputy Sirri Sakik, a militant Kurd activist, described the action by the authorities as "a step backwards in the country's democratic process as well as the process of integration with the European Union."

"Turkey is becoming a cemetery of banned political parties. Closing a group does not resolve the problem," he told AFP.

The Kurdish issue has returned to the international spotlight in recent weeks after the Turkish parliament approved cross-border strikes on PKK bases in northern Iraq. Turkey has massed 100,000 troops on the border and scores of PKK rebels have been reported killed in clashes in recent weeks in Turkish territory.

A series of Kurdish parties have been banned in recent years. The best known has been the Democratic Party. Four party lawmakers spent 10 years in jail up to 2004 because of alleged links to the PKK. One of them, Leyla Zana, was given the European parliament's Sakharov human rights award while in prison.

Pro-Kurdish parties have never, in their own right, got past the 10 percent of the vote needed to secure seats in parliament.

About 20 pro-Kurdish candidates who stood as independents in the national election in July grouped together in parliament under the DTP banner.

The ruling Justice and Development Party (AKP) won an overwhelming share of seats from the main Kurdish regions of southeast Turkey in the election.

The party has been accused by the government, opposition, army and the Turkish media of being the political wing of the PKK, which has been fighting the Turkish army since 1984 and is labelled a terrorist organisation by Turkey and the United States.

The DTP's new leader, Nurettin Demirtas, has spent more than 10 years in jail for belonging to the PKK.

Another deputy, Sabahat Tuncel, is on trial -- despite his parliamentary immunity -- for alleged support for the PKK while the husband of another deputy, Fatma Kurtulan, is a PKK fighter.

Nationalist deputies have demanded that the government end the immunity from prosecution for DTP lawmakers but even Prime Minister Recep Tayyip Erdogan has opposed this.

Senior prosecutor Abdurrahman Yalcinkaya has been working for the past year on a case against the DTP, which held a congress in Ankara last week to elect a leadership.

The legal procedure against the DTP is expected to take several months.

A poll conducted by Pollmark and published Friday indicated that 77.1 percent of all Turks opposed the DTP presence in parliament. That figure rose to 80.4 percent among those who defined themselves as ethnic Turks, but fell to 48.1 percent among ethnic Kurds.

The poll of 3,000 people across Turkey showed that 81.2 percent favoured a military operation against PKK rebels in northern Iraq, with just 13 percent opposed.