Armed bandits stormed a mining site in a remote village late Wednesday shooting at residents, Mohammed Shehu, a spokesman for the Kaduna State police told CNN."They ambushed 16 illegal gold miners and shot at them. Four people who heard the gunshots and ran to the site to assist were killed. They attacked another village and killed six people," Shehu said.Dozens of armed men stormed Kuru Kuru village Wednesday evening, demanding gold from miners before opening fire, one resident said. "They came when the miners were coming from the forest in the evening and started shooting asking for gold. They shot at everyone in sight as they escaped," Amisu Ahiru told CNN. Zamfara State Commissioner for Information, Muhammed Danjari, told CNN a mass burial was held for those killed Thursday."These attacks are very frequent and we need help," Danjari told CNN, saying 32 people were killed in a similar attack last month.Nigeria's President Muhammadu Buhari visited Zamfara last month to console families and communities that suffered from violent clashes in the state.Armed robbery has been a long-running problem in Zamfara's gold mining communities where artisanal mining poses environmental and health hazards to residents.A Médecins Sans Frontières report estimates 400 children died of exposure to lead and 30,000 others were poisoned in the northwestern state in the world's worst recorded outbreak of lead poisoning in 2012.