With Russia's war against Ukraine in its third year and energy and food prices much higher, support for the anti-immigration and eurosceptic National Rally (RN) party has surged despite President Emmanuel Macron's pledges to prevent its ascent.

Polling stations opened across mainland France at 8:00 am (0600 GMT) and will close 12 hours later, immediately followed by projections that usually predict the result with a degree of accuracy.

Voters in France's overseas territories that span the globe cast ballots earlier in the weekend. Some 49 million people are eligible to vote.

Elections for the 577 seats in the National Assembly are a two-round process. The shape of the new parliament will become clear after the second round on July 7.

Most polls show the RN on course to win the largest number of seats in the National Assembly, parliament's lower house, although it remains unclear if the party will secure an outright majority.

A high turnout is predicted and final opinion polls have given the RN between 35 percent and 37 percent of the vote, against 27.5-29 percent for the left-wing New Popular Front alliance and 20-21 percent for Macron's centrist camp.

If the RN obtains an absolute majority, party chief Jordan Bardella, Le Pen's 28-year-old protege with no governing experience, could become prime minister in a tense "cohabitation" with Macron.

On Monday, Macron plans to convene a government meeting to decide the further course of action, government sources told AFP.

France is heading for a year of political chaos and confusion with a hung Assembly, said Mujtaba Rahman, Europe head at Eurasia Group, a risk consultancy.

"There is no precedent in recent French politics for such an impasse," Rahman said.

Calls to mobilise 

Macron's decision to call the snap vote after the RN's strong showing in European Parliament elections this month stunned friends and foes and sparked uncertainty in Europe's second-biggest economy.

The Paris stock exchange suffered its biggest monthly decline in two years in June, dropping by 6.4 percent, according to figures released on Friday.

In an editorial, the French daily Le Monde said it was time to mobilize against the far right.

"Yielding any power to it means nothing less than taking the risk of seeing everything that has been built and conquered over more than two and a half centuries gradually being undone," it said.

 Spike in hate speech 

Many have pointed to a spike in hate speech, intolerance, and racism during the charged campaign. A video of two RN supporters verbally assaulting a black woman has gone viral in recent days.

Macron has deplored "racism or anti-Semitism".

He apparently hoped to catch political opponents off guard by presenting voters with a crucial choice about France's future, but observers say he might have lost his gamble.

Support for Macron's centrist camp has collapsed, while left-wing parties put their bickering aside to form the New Popular Front, in a nod to an alliance founded in 1936 to combat fascism.

Analysts say Le Pen's years-long efforts to clean up the image of a party co-founded by a former Waffen SS member have been paying off.

The party has promised to bolster purchasing power, curb immigration, and boost law and order.

A defiant Macron has stood by his decision to call the elections while warning voters that a win by the far right or hard left could spark a "civil war".

He has insisted he will serve out the remainder of his second term until 2027, no matter which party wins.