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.

Nicolás Maduro took the oath before parliament, vowing his third six-year term in office would be a "period of peace".

Venezuelan President Nicolás Maduro was sworn in for a third six-year term Friday despite international condemnation of his recent reelection as illegitimate, as his administration grows increasingly brazen in cracking down on opponents.