The EU announced "formal infringement proceedings" against Elon Musk's platform X on Monday, under a law designed to combat disinformation and hate after identifying suspect posts related to Hamas's October 7 attack in Israel.

The action against the company formerly known as Twitter is the first against a major online platform since Brussels implemented the Digital Services Act (DSA), a sweeping piece of European Union legislation that strengthens online companies' responsibility for content moderation.

"Today's opening of formal proceedings against X makes it clear that, with the DSA, the time of big online platforms behaving like they are 'too big to care' has come to an end," said the bloc's digital enforcer, EU commissioner Thierry Breton.

"We will now start an in-depth investigation of X's compliance with the DSA obligations concerning countering the dissemination and amplification of illegal content and disinformation in the EU, transparency of the platforms and design of the user interface."

X, in a statement on its platform, said it "remains committed to complying with the Digital Services Act and is cooperating with the regulatory process."

The European Commission said a preliminary information-gathering investigation it launched against X in October, which included looking at "the dissemination of illegal content in the context of Hamas' terrorist attacks against Israel," led to Monday's probe.

On the basis of that information, "the Commission has decided to open formal infringement proceedings against X under the Digital Services Act," it said.

The formal probe will examine four areas: the dissemination of illegal content; the effectiveness of X's efforts to combat disinformation; suspected restrictions on giving researchers access to its data; and suspected deceptive practices – known as "dark patterns" – related to its "Blue Tick" subscriptions.

In the event of proven infringements, the DSA carries penalties that can include fines going up to six percent of an online company's global revenues.

For serious and repeated violations, the EU can ban a platform operating in the 27-nation bloc.

The commission said that, under the formal probe against X, it would now "continue to gather evidence, for example by sending additional requests for information, conducting interviews or inspections."

It noted that the proceedings gave it powers to order X to undertake interim or remedial steps, pending the conclusion of the probe.

There is no deadline for the proceedings to wrap up.

Weeks after starting its initial information-gathering exercise against X, the commission also launched preliminary investigations along the same lines against TikTok, YouTube and Facebook owner Meta.

Those investigations also looked at how the platforms handled disinformation and illegal content related to the Hamas attack.

The Hamas attack on October 7 killed around 1,140 people in Israel, most of them civilians, and took an estimated 250 people hostage, of whom 105 have been released and several killed, according to the latest Israeli figures.

Israel retaliated with an intense bombardment of the Gaza Strip, which is controlled by Hamas.

More than 19,400 Palestinians, mostly women and children, have been killed in the Gaza Strip in Israeli bombardments since October 7, according to the Hamas government's health ministry, and much of the besieged territory has been reduced to rubble. (AFP)