On their return, angry Turkish nationalists stopped the convoy at a makeshift roadblock, set car tires on fire and smashed the windows of the buses with stones, video showed. Several demonstrators were injured, according to news reports.
Nationalist Turks oppose any concessions toward Kurdish rebels who have been fighting for autonomy in southeast Turkey in a conflict that claimed the lives of 37,000 people since 1984.
Ocalan's Kurdish rebel group, the Kurdistan Workers Party, or PKK, announced a unilateral cease-fire on Aug. 19 after Prime Minister Recep Tayyip Erdogan vowed to improve economic conditions in predominantly Kurdish areas and offer greater cultural freedoms for Kurds.
Turkish military officials have said they will fight until all rebels surrender or are killed.
A senior rebel commander, Murat Karayilan, said he would not be "held responsible" if violence increased after the one-month cease-fire expired on Sept. 20, pro-Kurdish Ozgur Gundem newspaper reported.