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.

Venezuela's President Nicolas Maduro, whose nearly 12 years in office have been marked by a deep economic and social crisis, was sworn in for his third term on Friday, remaining in power despite a six-month-long dispute over a contested July election and international calls for him to stand aside.

Venezuelan President Nicolás Maduro will be sworn in for a third six-year term after a reelection widely viewed as illegitimate and as his administration grows increasingly brazen in cracking down on its opponents.