By BY LUIS BOLIVAR AND KEVIN G. HALL
  Knight Ridder News Service

  LA PAZ, Bolivia - Tanks formed an iron curtain in front of Bolivia's presidential palace Thursday as a second day of violent protests swept the Andean
  nation and calls grew for President Gonzalo Sánchez de Lozada to resign.

  The violence was sparked by a clash between police and soldiers after most of La Paz's 7,000 police officers walked off the job and led protests
  Wednesday. They were joined by citizens angry over an unpopular income tax proposal.

  Over the two days, 22 people were killed, including at least nine police officers, and 102 were injured, according to Eduardo Chavez, director of La Paz's
  General Hospital, where most of the casualties were treated.

  Most of the disturbances Thursday were confined to the capital. Later in the day calm prevailed as striking police officers returned to their posts.

  In a nationally televised speech Thursday night, Sánchez de Lozada expressed his condolences to the families of the dead and called on citizens to resolve
  their problems through dialogue and not through violence.

  ''Democracy is not perfect. God knows it is not,'' Sánchez de Lozada said. ``Hopefully together we can find solutions to our grave problems, but we'll never
  find them through violence, looting and destruction.''

  The 72-year-old Sánchez de Lozada, known by his nickname Goni, made it clear he would not resign.

  However, the prospect for more turmoil that could threaten political stability remained high, analysts said.

  ''The worst-case scenario has played out and it's unlikely to get any better,'' said Eduardo Gamarra, director of the Latin American and Caribbean Center at
  Florida International University in Miami-Dade. ``This is the biggest challenge Bolivia's democracy has faced in 20 years. I don't think the protests will stop
  until [the opposition] gets the president to step down.''

  Bolivian government officials disputed the gloomy outlook.

  ''Order has been restored,'' Carlos Sánchez-Berzain, the minister of presidency, a position similar to chief of staff, told The Herald by telephone. ``What
  happened here had no political aspects tied to it. There is no reason for the president to resign.''

  As police worked to restore order in La Paz, disturbances erupted in other parts of the country, where officers had also left their posts. In Cochabamba,
  155 miles southeast of La Paz, rioters set fires in the street and shut down public transportation throughout the city.

  Leading the opposition effort is Evo Morales, who came close to winning the presidency last year and whose Movement to Socialism Party now controls
  about a third of Congress.

  Morales champions poor, mostly indigenous farmers who grow coca, the plant from which cocaine is made.

  In a heated address to demonstrators in La Paz's Plaza de San Francisco on Thursday, Morales called for nationwide highway blockages and civil unrest.

  ''We will not allow these deaths to go unpunished, we will not allow our natural resources to leave the country, we seek the resignation of the president of
  the republic,'' Morales told thousands of supporters.

  Morales, who represents cocaleros, wants an end to forced eradication of coca in the Chapare, a New Jersey-sized swath of tropical Bolivia where coca is
  not native but was brought by drug traffickers.

  Campaigning for president last year, Morales promised to eject the Drug Enforcement Administration from Bolivia if elected and to allow coca to be freely
  grown.

  Bolivia's crackdown on illicit coca is believed to have taken more than $200 million annually out of the economy of South America's poorest nation.

  The 12 percent tax proposal that drove people into the streets, and was withdrawn by the president in a bid for calm, affected anyone who made two
  times more than the monthly minimum wage of $58.

  The proposal, which requires congressional approval, was part of an economic package to help boost an ailing economy.

  Bolivia, which has been in a recession for the past four years and relies heavily on interna-tional aid, has a deficit of 8.6 percent of GDP, ''which means the
  country is bankrupt,'' Gamarra said.

  The International Monetary Fund has imposed a three-point reduction, and raising taxes is the most efficient method to meet that requirement without
  resorting to additional foreign borrowing, Gamarra said.

  Herald staff writer Nancy San Martin contributed to this report. Bolívar reported from La Paz and Hall from Rio de Janeiro.