Facebook CEO Mark Zuckerberg announced new steps to counter fake news on the platform on Saturday, marking a departure from his skepticism that online misinformation is, as Barack Obama said this week, a threat to democratic institutions.

“We take misinformation seriously,” Zuckerberg wrote in a post on Saturday. “We know people want accurate information. We’ve been working on this problem for a long time and we take this responsibility seriously.”

Zuckerberg said the company has “relied on our community to help us understand what is fake and what is not”, citing a tool to report false links and shared material from fact-checking sites. “Similar to clickbait, spam and scams, we penalize [misinformation] in News Feed so it’s much less likely to spread,” he wrote.

This summer Facebook fired the human team of curators who watched its “trending” news items, leaving its algorithm to sort links. Fake and misleading news proliferated further, and Facebook earned scorn for high-profile embarrassments, for instance the deletion of a Vietnam war photo deemed too graphic. On Saturday, Zuckerberg called the problem “complex, both technically and philosophically” and said the company erred “on the side of letting people share what they want whenever possible”.

“We do not want to be arbiters of truth ourselves, but instead rely on our community and trusted third parties.”

Facebook has “reached out” to “respected fact-checking organizations” for third-party verification, Zuckerberg said, though he did not provide specifics. He said the company also planned to make reporting false stories easier and to create “better technical systems to detect what people will flag as false before they do it themselves”.

Zuckerberg also said Facebook would experiment with warning labels on stories, and try to better screen the quality of links in the “related articles” section, where the site has linked to false conspiracy theories about the September 11 attacks and Michelle Obama, among others.

He also said the company was “looking into disrupting the economics” of fake news, conceding that misinformation was driven, at least in part, by people profiting off of Facebook’s ad mechanics.

The problem of misinformation online, once relegated to discussions of Russian propaganda, has drawn the attention of the president of the United States and the president-elect – albeit in different ways. On Thursday, Obama told reporters that the discrediting of news organizations and spread of misinformation threatened institutions.

“If we are not serious about facts and what’s true and what’s not, if we can’t discriminate between serious arguments and propaganda, then we have problems,” he said at press conference.

“If everything seems to be the same and no distinctions are made, then we won’t know what to protect,” he went on. “We won’t know what to fight for. And we can lose so much of what we’ve gained in terms of the kind of democratic freedoms and market-based economies and prosperity that we’ve come to take for granted.”

President-elect Donald Trump has meanwhile made Steve Bannon, former CEO of the website Breitbart News, his “chief strategist” in the White House. Under Bannon’s leadership, Breitbart frequently published stories with misleading and partisan bent, often with racist and misogynistic tones.

Only a week ago, Zuckerberg dismissed the “crazy idea” that fake news could influence voters, despite a BuzzFeed analysis showing that fake news on the site outperformed real news, and Pew research finding that most Americans get their news from Facebook and Twitter.

On Saturday, the CEO insisted fake news was still a marginal problem, echoing his previous remark that “more than 99% of what people see is authentic”.