President-elect Donald Trump says Venezuela's embattled opposition leader must be protected as President Nicolas Maduro takes the oath of office for a third six-year term.

Maria Corina Machado, a 57-year-old engineer with rock-star appeal, became the fearless figurehead of Venezuela's opposition after being barred from challenging strongman Nicolas Maduro in elections last July.

Machado was arrested by government security forces Thursday as she left a rally in Caracas on the eve of Maduro's inauguration after a widely discredited election.