Paris (AFP) - France on Wednesday issued a stern warning to Russia against meddling in its upcoming presidential elections, after US intelligence accused Moscow of interfering in America's vote to boost Donald Trump.

"We will not accept any interference whatsoever in our electoral process, whether by Russia or any other state," said Foreign Minister Jean-Marc Ayrault.

"After what happened in the United States, it is our responsibility to take all steps necessary to ensure that the integrity of our democratic process is fully respected," he told parliament.

The warning came as aides to one of the leading French candidates this week accused Russia of trying to derail his bid.

A spokesman for the staunchly pro-Europe Emmanuel Macron on Tuesday accused Moscow of being behind a flurry of cyberattacks on Macron's campaign website and email servers over the past month.

"Half of the attacks, and there are hundreds a day, come from Ukraine, which is known for its links to hackers and people responsible for cyberattacks in Russia," said Benjamin Griveaux, accusing the Kremlin of trying to boost conservative nominee Francois Fillon and far-right candidate Marine Le Pen, both of whom urge closer ties to Russia.

- Russia's favourites? -

Macron's aides have also accused the state-owned Russia Today (RT) channel and the Sputnik news agency of waging a smear campaign against the 39-year-old former economy minister.

They have pointed to a Sputnik interview with a pro-Fillon lawmaker titled "Ex-French Economy Minister Macron Could Be 'US Agent'" as an example of Russia's alleged bias. The article also quoted the lawmaker as saying Macron was backed by a "wealthy gay lobby".

Macron, who is married, last week denied rumours of having had a gay affair.

Speaking at the National Assembly, Ayrault also took aim at Fillon and Le Pen, saying it would be better if "certain candidates who see themselves favoured by, in particular, a country we know well -- Russia -- protest against this type of influence".

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Macron remains the front-runner in the presidential race, with 39 percent of those surveyed by Ipsos giving him a favourable opinion.

In the poll released by the magazine Le Point on Wednesday, Macron was followed by Socialist candidate Benoit Hamon, with 38 percent, while Fillon tumbled 18 percentage points to 25 percent, just behind Le Pen, at 26 percent.

Fillon's campaign has stumbled as it tries to fend off claims he used public funds while a senator to hire his wife and children for fake jobs.

- Denials from Moscow -

Moscow on Tuesday vehemently denied the Macron camp's allegations of meddling.

"We never had, and do not have, the intention of interfering in the domestic affairs of other countries, and especially not in their electoral process," Kremlin spokesman Dmitry Peskov said.

RT and Sputnik echoed the denial.

Earlier Wednesday, French President Francois Hollande asked his security cabinet to brief him on the "specific vigilance and protection measures being taken during the electoral campaign, including in the cyber domain", the presidency said.

Hollande, who is not himself seeking re-election, did not say what kind of threat the two-stage April 23-May 7 presidential election faces, nor did he point the finger at any group or country.

But the call comes in the midst of a furore over Russia's alleged interference in the US campaign that has already forced out one of Trump's top aides.

Trump's national security advisor Michael Flynn resigned on Monday after it was revealed that he misled top officials over his contacts with Russia during the campaign.

US intelligence agencies had already accused Russian intelligence of hacking Democratic Party emails that embarrassed Trump's rival Hillary Clinton.

German Chancellor Angela Merkel, whose country will hold a general election in September, has also voiced fears that Moscow could try to influence the vote through cyberattacks or disinformation.