A passenger bus late on Tuesday night hit a roadside bomb in Gach Kariz area of Maiwand district, said provincial police spokesman Jamal Nasir Barekzai.
At least five civilians were killed and 18 others wounded after the bomb went off, he said.
No one has claimed responsibility for the bombing.
Afghanistan, already gripped by decades-long war and violence, has been witnessing a rise in bomb attacks.
The attacks, often without claim of responsibility, claims lives of civilians mostly.
Follow TKG on Twitter & Facebook
