The U.S. Securities and Exchange Commission has sued billionaire Elon Musk, saying he failed to disclose his ownership of Twitter stock in a timely manner in early 2022, before buying the social media site.

Twitter's stock price rose 27 percent once Musk belatedly disclosed his stake, the lawsuit said. "During the period that Musk was required to publicly disclose his beneficial ownership but had failed to do so, he spent more than $500 million purchasing additional shares of Twitter common stock," it said.