Three protesters were killed and 30 wounded in clashes on Tuesday with Bolivian security forces lifting an opposition blockade of fuel supplies to La Paz, the public ombudsman's office reported.
Troops and police had moved to lift the siege on a fuel plant in El Alto by supporters of ex-president Evo Morales that has caused acute shortages in nearby La Paz.
A spokesman for the ombudsman's office said two of the dead had been hit by gunfire, including a 31-year-old man.
"We are asking the authorities for an investigation," the spokesman told AFP, adding that 30 people had been wounded, all of them supporters of Morales.
The army said in a statement that "agitators and vandals" had attacked and partially destroyed the Senkata fuel plant in El Alto, "using high-powered explosives."
The deaths bring to 27 the number of people killed since unrest began in the wake of October 20 elections, according to a tally by the Inter-American Commission on Human Rights.
A convoy of around 50 fuel tankers was able to leave the Senkata plant for the first time in more than a week after police and military forces using armoured vehicles secured the route to neighbouring La Paz.