Bolivian president Evo Morales has finalised contracts giving his government control over foreign energy companies' operations.
The deals, signed by the companies last month, also grant Mr Morales's government a majority share of the foreign companies' revenues generated in Bolivia.
This completes a process that began with the nationalisation in May of Bolivia's petroleum industry.
Foreign companies that signed contracts include Brazilian state energy giant Petroleo Brasileiro (Petrobras), Spanish-Argentine Repsol YPF, France's Total, and British Gas, a unit of BG Group.
Mr Morales also announced that Royal Dutch Shell had agreed to transfer to his government majority control of its Bolivian subsidiary, Transredes, which operates the country's largest network of gas pipelines.
Bolivia's natural gas reserves are South America's largest after Venezuela's.
"We thank the Bolivian people who have struggled to recover their natural resources," Mr Morales said in a signing ceremony at the presidential palace in the capital of La Paz.
"We have now completed the first step. This process will continue next year with the recovery of other natural resources benefiting the Bolivian people."
Mr Morales has said he also plans to nationalise Bolivia's mining sector.
Bolivia's first Indian president, Morales has vowed to reverse centuries of dominance by the country's European-descended minority, granting greater political and economic power to the poor indigenous majority.
AP