Police arrested seven Kurdish rebels on suspicion of involvement in a foiled bomb plot in Ankara last week.
Police detained the seven in the southeastern town of Baskale, local authorities said.
Some 600 kilograms - about 1,320 pounds - of explosives had been packed into a minibus discovered by Turkish authorities near an Ankara market on the sixth anniversary of the Sept. 11 attacks in the United States. Police defused the bomb.
Two other suspects were already under interrogation in Ankara.
Experts said the materials were similar to those seized in the past from Kurdish separatists.
Turkey accuses Kurdish rebels of smuggling explosives into the country from neighboring Iraq, where the guerrillas have been based for decades. Turkey is pressuring Iraq and the United States to crack down on the group in Iraq, and is threatening to do the job itself if others do not.