The 23-year-old E.P. said in his testimony he received orders from the Kurdistan Workers' Party (PKK) for last week's bombing in Diyarbakir following Turkish air raids on the rebel group's camps in neighbouring Iraq in December, police sources said.

He said the orders were relayed to him by two PKK militants, who also planned the attack and helped him with placing the explosives in a car and parking it in downtown Diyarbakir, the sources said.

The car bomb was detonated by remote control in central Diyarbakir on January 3, targeting a military vehicle with some 50 soldiers which was passing by.

Judicial officials involved in the probe confirmed the suspect had confessed to the attack. The blast claimed the lives of six people, among them five teenagers attending classes at a nearby private school, and left 67 people injured, including some 30 soldiers.

The police were looking for the two men the alleged bomber implicated.

Officials have already blamed the bombing on the PKK, which has waged a bloody 23-year campaign for Kurdish self-rule in the southeast.

The PKK, listed as a terrorist group by Ankara and much of the international community, apologised for the attack Tuesday and put the blame on Kurdish militants acting without the approval of the leadership.

One of the seven other suspects held by the Diyarbakir police was released without charges Thursday.

A judge is expected to question the suspects later this week and decide whether to formally charge them.

The alleged bomber was reportedly trained in explosives at PKK camps in northern Iraq before returning to Turkey in 2007.

He also confessed to hurling a hand grenade at a police station in Diyarbakir last year, the sources said.

Turkish army chief Yasar Buyukanit has described the Diyarbakir blast as a sign of "panic" in PKK ranks following the Turkish bombing raids on rebel bases in northern Iraq, where the group has long taken refuge.

The PKK had threatened to retaliate.

The army has confirmed three air raids conducted with US intelligence assistance against the PKK in Iraq since December 16 in which it said at least 150 rebels were killed and more than 200 PKK positions destroyed.

The PKK has waged a campaign for self-rule in mainly Kurdish southeast Turkey since 1984. The conflict has claimed more than 37,000 lives.