Erdal Polat, 24, had confessed to being a member of the outlawed Kurdistan Workers' Party (PKK) and obtaining the car used in the bombing, but denied detonating the vehicle.

The attack on January 3, 2008 in Diyarbakir, the largest city of Turkey's mainly Kurdish southeast, killed seven people -- six of them teenagers from a nearby private school. It wounded about 70 people, about half of them military officers.

The car exploded as an army bus was passing by with several dozen soldiers on board, on their way to a military facility.

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

The court sentenced five other suspects to six years and three months in jail each for helping Polat and for membership of the PKK. Six defendants were acquitted.

The prosecutor had argued that Polat was ordered to carry out the attack in retaliation for Turkish air raids against PKK hideouts in neighbouring Iraq.

The Turkish military has since December 2007 bombed rebel bases in northern Iraq, which the PKK uses as a launching pad for attacks on Turkish targets across the border.

The PKK took up arms for Kurdish self-rule in the southeast in 1984, sparking a conflict that has claimed about 44,000 lives.