Depicting the object of their ire as Napoleon, Dracula, Jupiter, a banker-king and Margaret Thatcher, tens of thousands marched through central Paris on Saturday to protest against President Emmanuel Macron's sweeping reforms, a year after he took office.

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Some 2000 security forces including riot police were deployed just in case a generally good-natured rally went the same way as May Day protests hijacked by anarchists.

Marchers gathered from midday in warm early summer sunshine in the central Opera square for a protest dubbed a "Party for Macron", a tongue-in-cheek "celebration" of the 40-year-old centrist and former Rothschild banker's first anniversary in power.

Paris police put the number of marchers at 40,000 but organisers said it was 160,000.

"It was not the huge influx that they had predicted," Interior Minister Gerard Collomb said, denouncing what he called an "attack" on an outside broadcast van of Franceinfo radio in the eastern quarter of Bastille, where the march ended.

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One of its windows was smashed and a smoke bomb thrown inside the vehicle.

"Luckily no journalist was inside when the smoke bomb was thrown," Collomb said.

One policeman was slightly injured by a projectile following the incident but there were none of the scenes of violence seen days earlier at a May Day rally and the atmosphere was festive ahead of a concert planned in the evening.

Eight people were arrested throughout the day, police said.

Smaller rallies took place in the southern cities of Toulouse and Bordeaux while the Paris one kicked off with a mass picnic which drew numerous families.

Organisers had urged participants to attend in a party mood - but the high security owed much to hundreds of black-clad youths having torched cars and a McDonald's restaurant during traditional May 1 demonstrations in the capital, prompting fears that more "black bloc" protesters could hijack Saturday's event.

One protester held aloft a placard with the words "Mac-ron is disgusting," a play on words to show his feelings about the president and the fastfood chain.

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'Worried about violence'

Government spokesman Benjamin Griveaux had expressed fears Friday that the demonstration could turn violent, hence the high security.

He noted that the protest's name, the "Fete a Macron", can have a double meaning in French - either celebrating someone, or trying to do them harm.

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Some supporters of the left-wing populist La France Insoumise party (LFI) brandished anti-Macron banners with slogans including "down with the president of the rich", "no to a social coup d'etat" and "for a Sixth Republic".

The protest is the latest in a series of large street demonstrations against Macron, whose overhauls of everything from the education system to the state rail operator have been causing friction with various groups.

It was organised by firebrand LFI lawmaker Francois Ruffin and other ex-members of the Nuit Debout (Up All Night) leftist movement that staged nocturnal rallies across France in 2016.

Ruffin told AFP this week that Macron may have won a democratic election last May but "democracy does not mean shutting up for five years".

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"People have the right to challenge him," said Ruffin, a journalist whose documentary "Merci Patron", about a poor couple who take on France's richest man, captured an angry zeitgeist and filled cinemas in 2015.

Some university faculties remain blocked by protests against Macron's plans to make university access more selective, causing major disruption to students starting their summer exams.

New rally on May 26

Friday marked the latest in a series of rail strikes as train drivers and other staff took a stand against Macron's overhaul of the SNCF, aimed at reducing its massive debts and making it more competitive.

Many French leftists have called for Macron's opponents, from students to striking rail workers, to join forces in a re-run of the massive May 1968 protest movement that shook France exactly half a century ago.

LFI leader Jean-Luc Melenchon said Saturday that many French people wanted to see "deep societal change".

Saying that "a new cycle of mobilisation has begun", Melenchon also lauded public sector workers who he said deserved more credit.

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Since he was elected a year ago, Macron has set about transforming France, taking on the unions and the employment laws.

Addressing supporters from a bus bearing the slogan "when everything is privatised we shall be deprived of everything", he warned Macron many people were sickened by "endless gifts for the rich (given) the difficulty of the French people to make ends meet".

Melenchon said Saturday was just the "first stage" of protests, announcing a new rally on May 26 and exhorting people to "turn up in their millions to become a human sea that will change history".