ANKARA, Turkey (AP) - A group of nationalist Turks attacked dozens of buses carrying pro-Kurdish demonstrators with stones on Sunday, following violent clashes between Kurdish demonstrators and police in Istanbul, reports said.

Tensions began Sunday morning when Kurdish demonstrators in Istanbul threw stones and firebombs during a rally to protest the solitary confinement of the imprisoned Kurdish rebel leader Abdullah Ocalan. Later, paramilitary police blocked thousands of other pro-Kurdish demonstrators loaded on buses from reaching the northwestern port town of Gemlik to stage an unauthorized demonstration. The port is used by Ocalan's lawyers to travel to the prison island of Imrali, where the rebel leader is the only inmate.

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.