French security forces briefly fired tear gas at opponents of the far-right marching in Paris on Saturday, according to a Reuters witness.
Demonstrators resumed their protests minutes later.
Macron and Le Pen came out on top in the 12-candidate first round. He received more than 27% and she came in second with about 23%.
Just 10 days ahead of a runoff election that will determine who will lead the European Union's second-largest economy for the next five years, opinion polls show centrist Macron is slightly ahead of far-right rival Le Pen. In 2016 Hollande, faced with very low ratings, decided not to seek reelection.
Relations between Hollande and Macron, his former economy minister, who quit the Socialist government to run for office in the 2017 presidential election on his own centrist platform, have not always been smooth.
Former right-wing president Nicolas Sarkozy had also backed Macron in the second round of the country's presidential election on April 24.
"I will vote for Emmanuel Macron because I believe he has the necessary experience faced with a grave international crisis ... his economic project puts the value of work as the top priority and his commitment to Europe is clear and unambiguous," Sarkozy posted on his Facebook page, pointing out that they must abandon the partisan habits.
"Fidelity to right-wing republican values and our governing culture must lead us to answer Emmanuel Macron's call for unity," he added.
