Tens of thousands of people have marched through Bolivia's administrative capital, La Paz, demanding the resignation of President Gonzalo Sanchez de Lozada.
Security forces fired tear gas at protesters
In one of the biggest protests since the crisis began, around 50,000 people - indigenous groups, farmers, workers and miners - took part in the street rally, in protest at government plans to export natural gas.
Angry protesters chanted insults and exploded dynamite sticks, while others shouted "Bolivia is not for sale" and threw stones when security forces attempted to disperse them with tear gas and rubber bullets.
Much of La Paz remains paralysed after weeks of blockades; there is little food or fuel, pharmacies are running out of basic medicines and there is no money in cash machines, Reuters news agency reported.
In another development, delegates from the Brazilian and Argentinian governments are expected in Bolivia on Friday to try to help resolve the conflict.
The Bolivian Government said it would receive the delegation, but the opposition said earlier this week that it would accept no mediation from other countries.
The protests resumed after the opposition rejected President Sanchez de Lozada's offer to hold a referendum on the gas project, saying it would accept nothing less than his resignation.
Dozens have been killed and injured in the protests
The Bolivian president has already been forced to postpone the controversial gas export scheme until 31 December.
Human rights groups estimate at least 65 people have been killed and dozens injured since demonstrations started more than a month ago.
But, says the BBC's Elliott Gotkine in Bolivia, this was never just about gas.
Bolivia is South America's poorest nation and the peasants want land reform, the elderly want better pensions and the workers want more money, he says.
The president's free-market reform strategy, centring on good relations with the United States, has bred particular resentment.
"The only thing the people want is this butcher's resignation," indigenous leader Felipe Quispe was quoted by Reuters news agency as telling a local radio station.
Mr Sanchez de Lozada's vice president, Carlos Mesa, has withdrawn his support for the president's policies and Minister of Economic Development Jorge Torres Oblea has resigned.
However the Bolivian leader remained defiant on Thursday, saying he was trying maintain democracy and rebuild the country.
He dismissed the unrest as a plot encouraged from abroad aimed at destroying Bolivia's democracy.
"It has not even passed through my mind to step down," he said.