A roadside bomb has killed at least four policemen and two civilians in southeastern Turkey.

The bomb, on a road in the Guroymak district of Bitlis province, exploded Tuesday as a police vehicle was passing by. The civilian victims included a two-year-old girl. Four people were wounded.

Authorities suspect Kurdish separatists were behind the attack. Security forces have been combing the area in search of the assailants, who are believed to be members of the outlawed Kurdistan Workers' Party, or PKK.

The PKK has escalated attacks against Turkish targets in recent months, carrying out a string of attacks in the southeast that have killed more than 50 Turkish personnel and civilians since July.

Turkish forces have responded by increasing their airstrikes against suspected rebel bases in northern Iraq. Last month, Turkey's military said it killed as many as 160 Kurdish rebels in air and artillery strikes across the border.

The rebels have waged a campaign for autonomy in Turkey's largely Kurdish southeast since 1984. The conflict has killed more than 40,000 people.