Brazil's first lady, Janja Lula da Silva, swore at billionaire Elon Musk during a G20 social event on Saturday at which she spoke about the need to regulate social media to rein in misinformation.

A ship's horn sounded as she spoke and she joked, "I think it's Elon Musk," before adding, "I'm not afraid of you, f... you, Elon Musk."

Musk, owner of social network X, reacted to a video of her remarks by posting a laughing out loud emoji graphic. In another post, he added, "They are going to lose the next election," in a reference to President Luiz Inacio Lula da Silva.

The president's wife spoke at an event ahead of the Rio de Janeiro summit of the G20 group of largest nations set for Monday and Tuesday.

Musk's social messaging network was suspended in Brazil for a month this year for failing to name a legal representative in the country and ignoring court orders to block accounts accused of spreading "fake news" and hate messages.