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 Nicolas Maduro regime arrested Venezuelan opposition leader María Corina Machado on Thursday after opening fire against the driver of the motorcycle in which she was riding, people close to her team said.

It is not viable for Venezuelan opposition leader Edmundo Gonzalez to enter the country, his ally Maria Corina Machado said on Friday, shortly after President Nicolas Maduro was sworn in for a third term despite months of controversy over the country's contested July election.