The Bolivian government confirmed on Sunday at least 16 deaths in clashes in the Amazonian province of Pando as the army attempted to impose martial law.
Local leaders said Sunday that the death toll could be as high as 25, though this was not immediately confirmed by authorities.
Luis Adolfo Mayar, a leader of the Single Federation of Peasant Workers in Pando, was quoted by the television network Erbol as saying that 25 people were killed, a further 25 injured and 106 remained missing after the clashes in the municipalities of Filadelfia and El Porvenir.
Due to the violence, the government of left-wing Bolivian President Evo Morales declared a state of siege Friday in Pando.
Both Morales and Interior Minister Alfredo Rada have called events in Filadelfia and El Porvenir a "massacre" and have said that hired killers - including some from Brazil and Peru - were used to attack local peasants.
Witnesses in Filadelfia said they were brutally hit, including women and children, and that many people fled into the jungle and remained missing Sunday.
A 17-year-old soldier was killed at the Cobija city airport by presumed assassins hired by the prefecture in rebellion against the central government.
Right-wing opposition groups in the resource-rich areas of the country began rising up late last week against the Morales administration's policies to redistribute wealth.
Regional forces demanding more autonomy and a greater share of profits from oil and gas production clashed with government troops in Pando, Santa Cruz, Tarija and Beni departments.
Pando Governor Leopoldo Fernandez and the Morales government accused each other for inciting the violence.
Morales last week expelled US ambassador Philip Goldberg, whom he accused of conspiring with Bolivian opposition groups to foment rebellion.
Provincial governors are demanding the restoration of the 30-percent local share of the tax on hydrocarbons, which Morales diverted to pay for his social agenda for the country's poor.
Morales said he was willing to discuss the tax issues and proposed constitutional amendments regarding regional autonomy.