Among the suspects is the alleged bomber, a 23-year-old man believed to be a member of the outlawed Kurdistan Workers' Party (PKK), and six others accused of helping him, the sources said.

The court released an eighth person who was not charged.

Police said they were questioning another man over the January 3 bombing in Diyarbakir, but gave no details on his identity or his connection to the attack.

Judicial officials say the suspected bomber has confessed to carrying out the bombing on orders from the PKK following Turkish air raids on the rebel group's camps in neighbouring Iraq last month.

Six people were killed and 67 others wounded when an explosives-laden car was set off by remote control near a military base in the centre of Diyarbakir as a military vehicle carrying 50 soldiers was passing.

Diyarbakir Governor Huseyin Avni Mutlu announced Friday that police had foiled a second bomb attack plotted by PKK militants in the city.

Officials have already blamed the January 3 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 last week and put the blame on Kurdish militants acting without the approval of the leadership.

The group had threatened to retaliate after the Turkish army carried out bombing raids on rebel bases in northern Iraq where thousands of militants have found refuge.

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.

Iraqi officials said Friday Turkish forces shelled areas across the border in northern Iraq.

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