An Afghan official says two sons and two nephews of a tribal leader were killed when a suicide bomber struck the family's car after prayers for a major Muslim holiday in northern Sari Pul province.

Zabi Amani, spokesman for the provincial governor, says the tribal leader, Rahim Khan, was not in the car at the time of the attack in Sangcharak district.

No group immediately claimed responsibility for Wednesday's attack, which came as Muslims worldwide celebrate Eid al-Fitr holiday that marks the end of the holy month of Ramadan.

Amani says the presumed target of the attack was Khan himself. He says another civilian was wounded in the bombing.

The Taliban have stepped up attacks against Afghan security forces, government officials and tribal leaders across the country.