Mark Zuckerberg says Facebook will share Russian-linked political ads with Congress

— -- After months of stonewalling, Facebook founder Mark Zuckerberg agreed to turn over more than 3,000 Russian-linked political ads that ran during last year’s election campaign to Congress.

In his remarks, made in a Facebook Live post from his personal account, Zuckerberg said the company “recently uncovered this activity” and began cooperating with investigators looking at Russian attempts to influence the 2016 presidential election.

“We are actively working with the US government on its ongoing investigations into Russian interference,” Zuckerberg said. “We have been investigating this for many months, and for a while we had found no evidence of fake accounts linked to Russia running ads. When we recently uncovered this activity, we provided that information to the special counsel. We also briefed Congress, and this morning I directed our team to provide the ads we've found to Congress as well.”

ABC News has learned that Zuckerberg called Sen. Mark Warner, D-Va, vice chair of the Senate Intelligence Committee, personally on Thursday to tell him of the company’s decision to offer more information to Congress.

The company conducted an inquiry into Russian election meddling in the spring but did not release its findings, raising concerns among leaders in the House and Senate that the social media giant was withholding information that could help them in the multiple ongoing investigations, according to the Washington Post.

In a recent interview with ABC News, Sen. Warner said Facebook initially denied to Congress that they had posted any ads paid by the Russians.

“When I raised these issues last winter, [they said] couldn’t happen and they privately said, you know, ‘Those are crazy ideas,’” Warner said. “Well, they weren’t crazy ideas.”

Warner was critical of Facebook’s efforts to account for Russian ads bought during the campaign, pointing out that the company’s initial report to Congress only covered ads purchased in Russian currency.

“There were lots of reports of [activity coming from] Albanian, Macedonia, Moldavia -- areas where there are some of these troll factories that were at least indirectly controlled by Russia,” Warner said. “I don't believe they looked at any of that.”

Russian companies spent more than $100,000 on the ads seen by millions of Americans.

Facebook’s chief security officer Alex Stamos says most of the ads did not mention a specific presidential candidate or the election, but focused on “amplifying divisive social and political messages” on immigration, gun rights and LGBT issues. Sen. Warner, however, says it’s clear that those divisive messages were “often stories that would help one candidate and potentially hurt another,” part of a broader effort the intelligence community has determined was designed to aid Donald Trump and hurt Hillary Clinton.

On Tuesday, Clinton mentioned the issue in an appearance on “The Late Show with Stephen Colbert.”

“I don’t think anybody can with a straight face say that the Russians did not set out to influence our election, and they did so,” Clinton said. “This latest revelation about the way they bought ads on Facebook and target them, we’re going to find out a lot more.”

Until today, Facebook had refused to reveal who paid for political ads, but Zuckerberg said the company will now hold itself to "an even higher standard of transparency" than television and other media and "strengthen our ad review process for political ads.”

“Going forward -- and perhaps the most important step we're taking -- we're going to make political advertising more transparent,” Zuckerberg said. “We're going to bring Facebook to an even higher standard of transparency. Not only will you have to disclose which page paid for an ad, but we will also make it so you can visit an advertiser's page and see the ads they're currently running to any audience on Facebook.”

Zuckerberg acknowledged that the company “won’t catch everyone immediately” but can only try to make it more difficult to use “bad content” to influence voters on its platform.

“I don’t want anyone to use our tools to undermine democracy,” he said. “That’s not what we stand for.”

ABC News’ Randy Kreider and Cho Park contributed to this story.