Following a high-profile probe seen as a test of EU resolve to police Big Tech, the social media platform owned by the world's richest person was slapped with a fine of 120 million euros ($140 million) on Friday for breaking the bloc's digital rules.

The penalty was swiftly criticized by the US administration of Donald Trump, who as president aligned with Musk on a contentious effort to slash the federal workforce and cut spending, before the two had a falling out.

Musk himself weighed in after the fine was announced, posting on his X account: "The EU should be abolished and sovereignty returned to individual countries, so that governments can better represent their people."

When a user reposted Musk's comment, he responded, "I mean it. Not kidding."

"I love Europe, but not the bureaucratic monster that is the EU," he added in another post.

The fine against X was the first imposed by the European Commission under its Digital Services Act (DSA) on content.

The Commission said X was guilty of breaching the DSA's transparency obligation.

The violations include the deceptive design of the platform's "blue checkmark" for supposedly verified accounts, and its failure to provide access to public data for researchers, it said.

X had also failed to be sufficiently transparent about its advertising, the Commission added.