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

Machado’s appearance at the rally was her first public appearance in months, since a government crackdown on Venezeulan opposition figures and their supporters last year.