The trial in Diyarbakir, the regional capital of the mainly Kurdish region, is seen as a major step in shedding light on allegations of widespread human rights abuses during Turkey's campaign to crush separatist Kurdish rebels.

Heavy security measures were in place for the hearing, with dozens of police on patrol around the courthouse and strict checks on spectators allowed inside, an AFP correspondent said.

The indictement said Colonel Colonel Cemal Temizoz set up a rogue unit that detained and questioned people for helping Kurdish rebels or to settle personal accounts when he was stationed in southeastern Sirnak province from 1993-1996.

Members of the unit, acting on orders from Temizoz, killed some of those questioned, often burying their bodies in shallow graves in uninhabited areas after taking their identification papers, the charge sheet added.

The unit "committed several crimes including premeditated murder and in the process used means and equipment provided by the state to facilitate the struggle against" rebels from the Kurdistan Workers' Party (PKK), it said.

The prosecutor was demanding life imprisonment with no chance of parole for all seven suspects which he held responsible for the murders of 20 people, the indictment said.

The indictment came after a series of excavations in the southeast of the country in March and April, as part of an investigation into allegations of extrajudicial killings by security forces, resulted in the discovery of bone fragments.

The investigation was launched after a former PKK member who later became an informer said in remarks published in the Turkish press that several people were went missing in the 1990s had in fact been executed summarily.

Some 45,000 people have been killed since the PKK took up arms for self-rule in the southeast.