He said a so-called sticky bomb was attached to a military vehicle and caused the explosion. No group claimed responsibility for the bombing, but the Taliban have stepped up attacks across Afghanistan.
Separately, authorities on Monday confirmed the Taliban have overrun a police headquarters in the Dahna-e-Ghori district in northern Baghlan province.
There was no immediate word on casualties in Baghlan. The Taliban are claiming they killed and captured "many" policemen.