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.

Machado was released after a brief detention while leaving a protest in Caracas Thursday on the eve of President Nicolas Maduro’s inauguration.

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.