The European Union has publicly said that it accuses X, formerly known as Twitter, of violating its regulations in areas such as combating unlawful content and misinformation.
In a post on the social networking platform, digital commissioner Thierry Breton detailed the alleged violations.
Elon Musk's X, he added, was likewise accused of failing to meet its transparency standards.
X stated that it is "cooperating with the regulatory process."
The company stated in a statement that it is "critical that this process remains free of political influence and follows the law."
"X is focused on creating a safe and inclusive environment for all users on our platform while protecting freedom of expression, and we will continue to work tirelessly towards this goal," the statement said.
These are the first official actions brought under the Digital Services Act (DSA), the EU's severe new laws for large digital businesses.
The DSA imposes additional requirements on big corporations to safeguard consumers from extremist material. If they do comply, they may be fined or suspended.
"Today, we opened formal proceedings against X based on several suspected infringements of the Digital Services Act," said EU Commission spokesperson Johannes Bahrke.
"With the initiation of proceedings, the Commission will now investigate X's systems and policies about certain suspected infringements." It has no bearing on the result of the inquiry."