European regulator Thierry Breton shared a letter to Meta CEO Mark Zuckerberg on Wednesday urging the billionaire to be "vigilant" about removing disinformation on his company's platforms during the ongoing Israel-Hamas conflict and ahead of upcoming elections.

Breton, European commissioner for the internal market, said the European Union has been seeing an increase in illegal content and disinformation on "certain platforms" following the Hamas attack on Israel. Meta owns popular social media platforms like Instagram and Facebook, as well as Threads, the company's competitor for X, formerly known as Twitter.

Under the EU's newly enacted Digital Services Act, Meta is responsible for monitoring and removing illegal content like terrorist content or illegal hate speech. The company also has to detail its protocols for doing so. Failure to comply with the European regulations around illegal content could result in fines worth 6% of a company's annual revenue.

"I urgently invite you to ensure that your systems are effective," Breton wrote in the letter, asking Zuckerberg to respond within the next 24 hours.

"After the terrorist attacks by Hamas on Israel on Saturday, we quickly established a special operations center staffed with experts, including fluent Hebrew and Arabic speakers, to closely monitor and respond to this rapidly evolving situation," a Meta spokesperson told CNBC. "Our teams are working around the clock to keep our platforms safe, take action on content that violates our policies or local law, and coordinate with third-party fact checkers in the region to limit the spread of misinformation. We'll continue this work as this conflict unfolds."

Breton shared a similar letter addressed to Elon Musk, the owner of X, on Tuesday, which included a stern warning for Musk. Breton wrote that his office has "indications" that groups are spreading misinformation and "violent and terrorist" content about the Israel-Hamas conflict on the platform.