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.

The inauguration of Venezuelan President Nicolás Maduro has left his opponents grappling with conflicting feelings of hope and disappointment, pondering why the leftist leader could not be stopped despite credible evidence that he had lost the election last year.

Venezuela opposition leader Maria Corina Machado was detained at a march in Caracas on Thursday in her first public appearance in months and her ally, former presidential candidate Edmundo Gonzalez, demanded she be freed immediately.