President Emmanuel Macron met billionaire businessman Elon Musk on Monday to discuss future investment projects, as the French leader hosts a conference aimed at persuading business leaders to put their money in France.

Macron hosted the world's second richest man, who is the chief executive of electric car firm Tesla, social media company Twitter and cosmic exploration outfit SpaceX, six months after their last encounter in the United States, his office said.

They met at the Elysee Palace before both head to Versailles for the latest edition of the president's Choose France conference where Macron seeks to drum up investment in the country.

The two men were to talk about the "attractiveness of France and its industries", Macron's office announced. Musk smiled and waved at reporters as the meeting got underway but made no comment. 

Finance Minister Bruno Le Maire told the BFMTV broadcaster that "negotiations are ongoing" with the magnate.

Le Maire gave no details of Monday's talks with Musk, saying simply that "all of today's investments are the fruit of months or even years of negotiations".

During a US trip in December, Macron held an unannounced face-to-face meeting with Musk, saying later the two had had a "clear and honest" discussion during an hour-long meeting, including on electric cars and batteries.

He had also conveyed to Musk his - and Europe's - concerns about content moderation on Twitter since Musk bought the influential platform.

"Transparent user policies, significant reinforcement of content moderation and protection of freedom of speech: efforts have to be made by Twitter to comply with European regulations," Macron tweeted after that meeting.