Supporters of Bolivia's leftist President Evo Morales clashed with opposition protesters striking over constitutional reform plans, injuring at least 10 people, local media said.
Businesses and schools shut down in Santa Cruz, Bolivia's most populous city, as part of the 24-hour general strike staged in four of the South American country's nine provinces in the biggest challenge yet to Morales' leadership.
The government of Morales, who became Bolivia's first Indian president after years leading street protests, played down the strike, while the rightist opposition Podemos party said the regions had been "paralyzed."
"This is a historic day of struggle for democracy and against authoritarianism," German Antelo, a leading Santa Cruz autonomy advocate and strike leader, said in denouncing the violence, which he linked to the government.
Interior Minister Alicia Munoz said the strike was "a total political failure" because few Bolivians took part. The most violent clashes between Morales' supporters and opposition protesters took place on the outskirts of the eastern city of Santa Cruz, Bolivia's economic powerhouse and the leading voice among four provinces that want greater autonomy from the central government.
Protesters attacked the local offices of the state television channel with Molotov cocktails in the early hours, television pictures showed.
In downtown Santa Cruz, shops and schools were shut, streets were empty, public transportation was at a standstill and protesters blocked main roads into the city, the reports said. Regional leaders said natural gas exports would not be affected by the strike.
In May, Morales nationalized the energy industry in unstable Bolivia, which has South America's biggest natural gas reserves after Venezuela but is its poorest country.
Constitutional reform is a central demand of the indigenous majority, which helped elect Morales in December. He says rewriting the country's constitution will help end centuries of domination by a rich, European-descended elite.
The rightist leaders and four pro-autonomy provinces are unhappy with plans they say could entrench a leftist, indigenous agenda. With a year to carry out the constitutional reform, an elected national assembly took office last month.
Morales allies, who hold 56 percent of its seats, voted in the absence of opposition delegates this week in favor of a simple majority voting system in the assembly. The opposition, which wants a two-thirds majority system, accused the ruling party of "dealing a blow to democracy."