The bullets struck electric decorations that triggered a short-circuit, igniting a women-only marquee at the wedding on Tuesday night in Eastern Province, said Al-Yaoum newspaper, citing civil defense chief General Abdullah Khsheiman.
Al-Yaoum, which is based in the province, said at least 28 people died in the fire, although various other reports put the death toll at 25, all of them women and children.
The governor of the oil-rich region, Prince Mohammed bin Fahd bin Abdul Aziz, ordered a prompt investigation into the incident, the Okaz daily reported.
Only women and small children were in the tent in line with strict rules of segregation in the ultra-conservative Muslim kingdom.
In July 1999, 76 people died in a similar incident in Eastern Province.