A suspect was apprehended late Tuesday in Diyarbakir, the country's main Kurdish city, where an explosives-laden car went off Thursday, killing six people and wounding 67 others, the sources said.

He is believed to have helped the alleged perpetrator of the attack, a suspected militant of the separatist Kurdistan Workers' Party (PKK) who was detained in Diyarbakir Monday, Anatolia news agency reported.

The second suspect was detained in a village near Van, about 380 kilometres (235 miles) northeast of Diyarbakir, an aide to the local prosecutor said.

The suspect was believed to be a PKK member, according to Anatolia.

About 55 kilogrammes (121 pounds) of explosives were seized in a vehicle abandoned outside Van a day after the Diyarbakir blast and the local police received a tip-off that bomb attacks were planned there as well.

The car bomb in Diyarbakir was detonated by remote control as an army vehicle with some 50 soldiers on board was passing by.

Five of the six victims were teenagers attending classes at a nearby private school training students for university exams. About 30 of the injured were soldiers.

Officials have 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 on their own.

The alleged bomber was trained in explosives in PKK camps in neighbouring northern Iraq, where the rebels take refuge, media reports said.

The six other suspects held in the probe hail from the same family and are related to the suspected assailant, judicial officials said.

Army chief Yasar Buyukanit has described the Diyarbakir blast as a sign of "panic" in PKK ranks following Turkish air strikes in December on rebel bases in northern Iraq, against which the PKK had threatened to retaliate.

The military 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.

More than 37,000 people have been killed since the group took up arms in 1984.