Hundreds of thousands of people have marched in Paris and cities across France to protest against the country's far-right party National Rally (RN) ahead of upcoming elections to the French parliament.

President Emmanuel Macron called the snap elections, to be held in two rounds on June 30 and July 7, after his centrist alliance was trounced by the RN in last Sunday's European Parliament ballot.

The French Interior Ministry said 250,000 people turned out to oppose the RN on Saturday, including 75,000 in Paris. 

Despite rainy and windy weather, those who fear that the elections will produce France's first far-right government since World War II gathered at Place de la République before marching through eastern Paris. 

Up to 21,000 police and gendarmes were deployed in the capital.

Protesters held placards reading "Liberty for all, Equality for all and Fraternity with all" — a reference to France's national motto — and "Let's break frontiers, documents for all, no to the immigration bill". Some chanted "Free Palestine, viva Palestina" and wore keffiyeh scarves.

Speaking at Place de la République, hard-left CGT union leader Sophie Binet told reporters: "We are marching because we are extremely worried that [the RN's head] Jordan Bardella could become the next prime minister … We want to prevent this disaster."

Carol-Ann Juste, a 22-year-old student taking part in the Paris march, said it was the first time she had taken part in a protest. 

She said she was "worried because people believe the lies of this party that has a truly racist heritage", a reference to the National Front, a forerunner to the RN, whose leader Jean-Marie Le Pen was fined for remarks seen as anti-Semitic or xenophobic.

Ms Juste said she wanted to "fight to preserve a country of human rights, freedom, and tolerance".

On the same march, Cecilia Lormeau, a 34-year-old teacher who said she planned to vote for the Popular Front, an alliance of left-wing parties, said: "It is important to show we are mobilised and that the RN is not the majority of the people."