One person was killed and three others sustained injuries as a blast hit Khost city, capital of Khost province, 150 km southeast of Kabul on Saturday, a local official said.
"The bomb planted on a road in Takhtabig area on the outskirts of Khost city and went off next to a police van, leaving one police dead and injuring three others," spokesman for the provincial government Mubariz Zadran told reporters.
Blaming Taliban militants for the attack, the official said efforts are underway to bring to justice those behind the bombing.
Taliban militants who are largely relying on suicide and roadside bombings are yet to claim responsibility.