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.

Maria Corina Machado, a 57-year-old engineer with rock-star appeal, became the fearless figurehead of Venezuela's opposition after being barred from challenging strongman Nicolas Maduro in elections last July.