Facebook boss Mark Zuckerberg has said the social network "didn't do enough" to protect user data in a written statement to the US Congress.

Ahead of appearances before US Congress committees on Tuesday and Wednesday, Mr Zuckerberg said he took responsibility for recent Cambridge Analytica data scandal, as well as the platform's issues with fake news and abusive content.

Facebook has confirmed it believes up to 87 million people had their data harvested by the political consultancy via a personality quiz app.

The company is schedule to start notifying users as of Monday, with a detailed message appearing on the news feed of those who might have had their data shared.

Facebook says more than 70 million of the affected users are in the US, though there are over a million each in the Philippines, Indonesia and the UK.

In addition, all 2.2 billion Facebook users will receive a notice titled "Protecting Your Information" with a link to see what apps they use and what information they have shared with those apps.

If they want, they can shut off apps individually or turn off third-party access to their apps completely.

'We didn't do enough'

Mr Zuckerberg acknowledged that he made a "huge mistake" in failing to take a broad enough view of what Facebook's responsibility is in the world

"It's clear now that we didn't do enough to prevent these tools from being used for harm as well," Mr Zuckerberg's written statement said of the platform.

"That goes for fake news, foreign interference in elections, and hate speech, as well as developers and data privacy. We didn't take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and I'm sorry. I started Facebook, I run it, and I'm responsible for what happens here.

"So now we have to go through every part of our relationship with people and make sure we're taking a broad enough view of our responsibility."

The social network's founder and chief executive also said the site did not spot Russian propaganda and misinformation quickly enough.

He said the company now estimates around 126 million people may have seen content from the Internet Research Agency (IRA), a Russian propaganda organisation which generated around 80,000 Facebook posts over a two-year period.