LA PAZ, Bolivia (AP) — Striking Bolivian miners kidnapped and beat to death the country's deputy interior minister in a shocking spasm of violence following weeks of tension over dwindling paychecks in a region hit hard by falling metal prices. The miners were demanding they be allowed to work for private companies, who promise to put more cash in their pockets.

The issue has bedeviled President Evo Morales, who began as a champion of the working class and privatized the nation's mining industry, only to see his support crater amid the downturn. Miners say Morales has become a shill of the rich, and done little to help them make ends meet as the economy slows.

Deputy Minister Rodolfo Illanes, whose formal title is vice minister of the interior regime, had traveled Thursday to the scene of the violent protests in an effort to negotiate with the strikers who armed themselves with dynamite and seized several highways.

Instead, Illanes was "savagely beaten" to death by miners, Defense Minister Reymi Ferreira told Red Uno television, his voice breaking.

Prosecutor Edwin Blanco Friday said an autopsy showed that Illanes died from trauma to the brain and thorax.

Government Minister Carlos Romero on Thursday called it a "cowardly and brutal killing."

Earlier in the day, Romero had said that Illanes had been kidnapped and possibly tortured, but wasn't able to confirm reports that he had been killed by the striking informal miners, who were demanding the right to associate with private companies, among other issues.

"This is a political conspiracy," Morales said at a news conference on Friday. Calling for three days of official mourning, he criticized the "cowardly attitude" of the protesters and insisted that his government had "always been open" to negotiation.

The fatal beating came after the killings of two protesters in clashes with police, deaths that likely fueled the tensions.

Illanes had gone to Panduro, 80 miles (130 kilometers) south of the La Paz, to open a dialogue with the striking miners, who have blockaded a highway there since Monday. Thousands of passengers and vehicles are stranded on roads blocked by the strikers.

Officials say he was taken hostage by the miners on Thursday morning. At midday, Illanes said on his Twitter account: "My health is fine, my family can be calm." There are reports that he had heart problems.

Bolivia's informal or artisan miners number about 100,000 and work in self-managed cooperatives. They want to be able to associate with private companies, but are currently prohibited from doing so. The government argues that if they associate with multinational companies they will no longer be cooperatives.

The National Federation of Mining Cooperatives of Bolivia, strong allies of Morales when metal prices were high, was organized in the 1980s amid growing unemployment in the sector that followed the closure of state mines.

Federation members went on an indefinite protest after negotiations over the mining legislation failed.