Facebook is rolling out its promised new disclosures on political advertising on Thursday — including so-called issue ads that were used by Russian-linked accounts to spread misinformation and chaos in the 2016 election.

The disclosures include a tag appended to ads that identify who paid for them. Advertisers will need to verify with Facebook, via mail, that they reside in the U.S. before they're permitted to run political ads targeted to Americans.

"We’re up against smart, creative and well-funded adversaries who change their tactics as and when we spot abuse," said Rob Leathern, Facebook's director of product management, in a blog post announcing the move. "But we believe that they will help prevent future interference in elections on Facebook."

Facebook has been harshly criticized since the 2016 race for allowing nefarious actors, including those tied to Russia, to use the platform to interfere in that contest. Russian-linked accounts made particular use of issue ads, which address political topics like gun control or immigration but don't mention a particular candidate or election contest.

Katie Harbath, Facebook's global politics and government outreach director, told reporters on a call Thursday that issue ads are an important part of the effort, saying, "After all, many of the Russian ads around the election focused on stirring passions on divisive issues" rather than on candidates.

Company officials said on the call they have heard concerns, including from news publishers, that their advertising might be inappropriately marked as issue ads. Facebook said it will maintain an archive of those ads so that the public, including academic researchers, will be able to judge its decision-making. "We'll keep working on the process and improve as we go," Harbath said.

Facebook users will be able to flag the company to ads that they believe to be political or issue-oriented but that lack the required disclosures. The company said it will roll out a tool next month that allows Facebook users to view every ad placed by an individual advertiser, including details on the budget for the ad campaign and its target audience. The tool is currently being tested in Canada, the company said.

The new disclosure features will also be available on Instagram, which is owned by Facebook.

Facebook initially scoffed at the idea that activity on its platform influenced the 2016 election that brought Donald Trump to the presidency, with CEO Mark Zuckerberg calling it a "pretty crazy idea" that fake news on Facebook had swung the vote. But the company has since taken a number of steps to address threats to the democratic process. The company has let users know if they engaged with Russian trolls on the site, and it says it's ramping up the use of artificial intelligence to identify fraudulent accounts.

Facebook's role in the election has drawn the scrutiny of Congress. Sens. Mark Warner (D-Va.), Amy Klobuchar (D-Minn.), and John McCain (R-Ariz.) have been championing a bill called the Honest Ads Act that would mandate disclosures on political and issue advertising online, but it has failed to gain traction.

Twitter announced earlier Thursday that it will introduce disclosure requirements on political ads this summer. The company said issue ads will be covered by "a separate upcoming policy."