French President Emmanuel Macron has announced plans for a new law to combat so-called fake news.
He said that during elections social media would face tougher rules over the content that they put online.
Deliberate attempts were being made to blur lines between truth and lies and undermine people's faith in liberal democracy, he added.
Correspondents say there is no question that Mr Macron had Russia in mind when he made the announcement.
He has already spoken out publicly about what he sees as Moscow's attempts to manipulate opinion in Europe and the United States.
Speaking at a new year reception for the media, Mr Macron said it was possible now at a cost of just a few thousand euros to propagate untruths over social media.
"Thousands of propaganda accounts on social networks are spreading all over the world, in all languages, lies invented to tarnish political officials, personalities, public figures, journalists," he said.
In response, he proposed imposing tougher rules on social media about revealing the sources of apparent news content.
He also said limits would be put on how much could be spent on sponsored news material.
"We will develop our legal system to protect democracy from this fake news," he said, quoted by AFP.
France's audiovisual regulator would be given extra powers to "fight any destabilisation attempt by television channels controlled or influenced by foreign states", he added.
Mr Macron denounced Russia media outlets RT and Sputnik at a joint news conference with Russian President Vladimir Putin last May, accusing them of spreading "deceitful propaganda".
Since then RT has launched a French-language TV channel.