Colonel Cemal Temizoz was detained in the central city of Kayseri, where he commands a regiment of gendarmerie (paramilitary police), as part of an inquiry that has been in progress for several weeks, it said.

In 1990 he was based at Silopi, a small town in the far southeast of Turkey, where recent searches ordered by the authorities turned up 20 fragments of bone and pieces of tissue in what the Turkish media have dubbed "death pits".

The investigation was launched in February after media published statements by a defector from the outlawed Kurdistan Workers' Party (PKK), blacklisted as a terrorist group by Turkey and much of the international community, who spoke of the alleged brutality of the intelligence services of the gendarmerie, the Jitem.

He claimed that the bodies of Kurds who collaborated with the rebels of the PKK, who seek an independent Kurdistan, were thrown into pits filled with acid or buried along the road between Silopi and another small town, Cizre.

Kamil Atak, the former mayor of Cizre, was arrested Saturday in a neighbouring province where he was hiding, a local legal source said. He belonged to a local Kurdish militia, "village guards", paid and armed by the Turkish state to combat the PKK.

An unidentified witness told the prosecutor in charge that the former mayor had handed over several people suspected of aiding the PKK to members of another outlawed group, the Islamist Turkish Hizbullah, who in turn killed them, the source said.

The Turkish Hizbullah, which has no known links to its Lebanese namesake, was set up in the early 1990s as a reaction to the PKK and is believed to have been used by Turkish authorities against the rebels.

Atak's son has been charged with murder and membership of an illegal armed organisation and was detained Friday as part of the same investigation.

The PKK took up arms for Kurdish self-rule in 1984, triggering a conflict with the Turkish state that has left 44,000 dead, displaced thousands and led to allegations of gross human rights violations by both sides.

Over the past 10 years the bodies of four missing people have been exhumed in the region, the most recent in 2005 by a roadside.