The mayors have been on trial since September over a letter they wrote to Danish Prime Minister Anders Fogh Rasmussen in December 2005, asking him to ignore Ankara's calls to ban the Denmark-based Kurdish television station Roj TV, which is allegedly linked to the rebels.

The prosecutor argued Tuesday that the defendants had "knowingly and willingly" supported the Kurdistan Workers' Party (PKK), which has waged a bloody separatist campaign against Ankara in the mainly Kurdish southeast since 1984.

The Turkish authorities say Roj TV is a mouthpiece of the PKK, listed as a terrorist group by Ankara, the European Union and the United States.

The prosecutor asked for jail terms of seven years and a half to 15 years for 53 mayors, all members of the Democratic Society Party, the main legal Kurdish political movement in Turkey.

Among them is Osman Baydemir, one of Turkey's most popular Kurdish politicians and mayor of Diyarbakir, the largest city in southeast Turkey.

Roj TV, the prosecutor said, regularly carries PKK statements and interviews with PKK commanders, thus "it is an indisputable fact that Roj TV is the mouthpiece of the PKK terrorist organisation and... serves its objectives."

He called for the acquittal of three mayors who said their names were placed among signatories on the letter without their knowledge.

The defendants, none of whom attended the hearing, have rejected the charges, saying the letter meant to defend freedom of the press and the interests of the Kurdish people in the southeast, where Roj TV enjoys a wide audience.

The mayors had written to Rasmussen that silencing Roj TV "would mean the loss of an important vehicle in the struggle for democracy and human rights" in Turkey.

They said efforts to press Denmark into banning the channel contradicted Turkey's commitment to improve its democracy record in its bid to join the European Union.

The court adjourned the hearing to May 8 for a possible verdict.

Kurdish politicians are traditionally suspected of supporting the PKK and are routinely prosecuted for alleged links to the group.

Roj TV has become a thorn in the side of Turkish-Danish relations.

During a visit to Copenhagen in November 2005, Turkish Prime Minister Recep Tayyip Erdogan boycotted a joint news conference with Rasmussen after the Dane rejected his request that a Roj TV reporter be barred from entry.

Danish authorities have said that Roj TV's programming contains no incitement to hatred of Turkey and there is no proof it is linked to the PKK.

Under EU pressure, Turkey has in recent years broadened Kurdish cultural freedoms, including the introduction of limited Kurdish-language television and radio broadcasts.

Kurdish activists, however, say the reforms are inadequate and have called notably for a general amnesty for PKK militants to encourage them to lay down their arms.