The attack and the discovery of the bomb comes at a time when police are on alert against heightened violence by Kurdish rebels before the Aug. 15 anniversary of their first attack on Turkish targets in 1984. Kurdish rebels have been fighting for autonomy in Turkey's southeast in a conflict that has killed as many as 40,000 people.

The state-run Anatolia news agency said suspected Kurdish rebels fired on the military convoy with long-range weapons late Thursday in the town of Yuksekova, close to the border with Iraq.

The military later increased its presence in Yuksekova, sending convoys of tanks driving through its streets in the night, an Anatolia video footage showed.

On Friday, police deactivated a bomb placed on a busy road some 100 meters from the headquarters of a riot police force, Anatolia and other news reports said.

The bomb was made of 3.5 kilograms of plastic explosives — a device similar to those used by rebels in the past, CNN-Turk television reported. Police would not comment on the reports.

The rebels belonging to the Kurdistan Workers' Party, or PKK, have been fighting for autonomy in Turkey's southeast.

They intensified their attacks since June, saying the government has rejected their calls for a dialogue. The group is considered a terrorist organization by the United States and the European Union.

Meanwhile, an Iranian conservative news website says clashes with Kurdish rebels in northwestern Iran have killed three members of the powerful Revolutionary Guards.

Friday's report by Tabnak website says the fighting took place midday Thursday near Orumieh, the provincial capital of West Azerbaijan. The mountainous province borders Turkey and has seen sporadic fighting between Iranian forces and the rebels.

The report says the guards clashed with members of the Party for Free Life in Kurdistan, or PEJAK, which says it is fighting for greater rights in Iran.  PEJAK is the Iranian wing of the PKK.

The report says a fourth Guard soldier was wounded. It gave no further details.