Washington, DC (CNN Business) So far this year, Facebook has shut down 5.4 billion fake accounts on its main platform, but millions likely remain, the social networking giant said Wednesday. That's compared to roughly 3.3 billion fake accounts removed in all of 2018.

As much as 5% of its monthly user base of nearly 2.5 billion consists of fake accounts, the company said, despite advances in technology that have allowed Facebook to catch more fake accounts the moment they are created.

The disclosure highlights the scale of the challenge before Facebook as it prepares for a high-stakes election season in the United States, as well as the 2020 US census. Analysts and watchdogs are bracing for a wave of fake and misleading content on social media following revelations about election meddling in 2016.

On a call with reporters, CEO Mark Zuckerberg framed the large number of fake accounts that have been removed as a sign of how seriously the company is taking this issue and called on other platforms to make similar disclosures.

"Because our numbers are high doesn't mean there's that much more harmful content. It just means we're working harder to identify this content and that's why it's higher," he said on Wednesday.

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