Donald Trump says Venezuela's embattled opposition leader must be protected, as President Nicolas Maduro prepares to take the oath again after allegedly stealing an election.

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.

Machado, a former lawmaker who has spearheaded the opposition to President Nicolas Maduro in recent years, was detained by security agents who shot at motorcycles she was using to leave a protest in Caracas, the capital, according to posts on social media from her party. She was freed about an hour later, according to the party.