Hecklers jeered François Hollande during war commemorations Tuesday, marring Remembrance Day and piling further misery on France's most unpopular president on record.
The unusual incident, which was condemned by the government and part of the opposition, came amid mounting nationwide discontent over stinging unemployment and rising taxes.
To the anger of others who had come to pay their respects to the millions killed in the 1914-18 war, protesters shouted "Hollande resign" and "Socialist dictatorship" as the president paraded up the Champs-Elysees.
"You have no right to exploit November 11. You're a disgrace for France!", one onlooker yelled at the protesters.
Scuffles broke out between protesters and security forces, and police said 73 people had been detained, some of whom are linked to far-right movements, including a group called the "French Spring" that opposes France's gay marriage law.
Some of those shouting slogans against Hollande were wearing the red headwear that has come to symbolize a growing feeling of despondency over rising taxes and record unemployment in France.
The so-called "red bonnet" movement emerged last month in the hard-hit agricultural region of Brittany, where people took to the streets wearing the hats in reference to a famous 17th-century "Red Bonnet Revolt" against tax rises.
But Christian Troadec, a spokesman for the Breton movement, condemned the Paris protesters, saying they had "nothing to do with our movement".
Hollande continued his procession along the capital's most famous avenue and laid a wreath of flowers in front of the Tomb of the Unknown Soldier, in memory of all the servicemen who died during the war.
A poll by research firm Ipsos published Monday showed only 21 percent of the French approve of his policies, down from 24 percent in October.
That makes Socialist Hollande the most disliked president since France switched to presidential politics more than half a century ago.
Later in the day, protesters once again heckled Hollande as he visited the town of Oyonnax in eastern France, this time to mark a rally staged by members of the French resistance on November 11, 1943 during World War II.
"It's not the day (to do this), true, but the current policies are really disappointing, there are many promises that have not been kept, life is expensive and we end up in the red at the end of the month," one protester told AFP.
Interior Minister Manuel Valls lambasted the protesters, whom he said "refused to respect a moment meant for reflecting and uniting".
The main opposition leader, right UMP chief Jean-Francois Cope, described the jibes against Hollande as "very regrettable" and added that "there is no room for political debate" at such remembrance events.
But he went on to accuse Hollande and his government of failing to acknowledge "a high level of exasperation" across the nation.
Far-right leader Marine Le Pen denied any ties to the hecklers and voiced outrage at Tuesday's arrests, several of which she charged had been made before the Paris event got under way.
Remembrance Day ceremonies were also disrupted in the southeastern town of Chateaurenard, where the mayor and two other people were assaulted and stabbed, police said.
The injuries of the three victims are not life-threatening. According to an initial probe, the attacker may have had mental health problems.