At least 12 people have been killed and 57 injured in Bolivia in clashes between state-employed and independent tin miners, the interior ministry said.
Mine workers used dynamite and firearms in a battle for control of the Huayuni mine in the Andes mountains, one of the largest tin mines in the world, Bolivian unions said on Thursday.
The army was sent to the region after hundreds of members of an independent miners co-operative took control of the state-owned mine early on Thursday.
Government employed miners attempted to fight back and clashes continued into the afternoon.
Juan Ramon Quintana, a presidential spokesman, called the fighting "demented and fratricidal" and appealed for calm.
Roberto Chavez, leader of the Bolivian Mine Workers Union Federation, blamed the government of Evo Morales, the president.
"Now, let them provide the caskets," he said, demanding that Walter Villarroel, the mining minister, resign.
Villaroel is to travel to the area in an effort to persuade both sides that they can work together at Huanuni, officials said.
Morales's government has negotiated an end to recent protests and road blockages over Indian rights, natural resources and land, and coca-leaf farming.
Late last month, state-paid miners blocked highways demanding more jobs in the Huanuni mine, halting the flow of vehicles through one of Bolivia's main trade routes for several days.
Huanuni, 280km south of La Paz, belongs to the state-run Corporacion Minera de Bolivia, or Comibol, and is the largest tin mine in South America.
Mining co-operatives, with about 63,000 members throughout the country, have demanded that they too be allowed to mine its tin deposits.