"Six people were killed and a dozen more were wounded, local health officials previously reported a much higher number of injured people," the spokesman said.
According to local sources, the explosion targeted the wedding ceremony of a local militia commander's son.
Local media reported that the bombing attack might have been perpetrated by a minor.
The attack took place in the province's Pachir Aw Agam district.
No militant group has so far claimed responsibility for the attack, but IS-K, which is the local branch of the Daesh* terrorist organization, and the Taliban movement are known to be active in the province.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia