By Scott Shane and Mike Isaac

New York Times News Service

WASHINGTON — Under growing pressure from Congress and the public to reveal more about the spread of covert Russian propaganda on Facebook, the company said Thursday that it was turning over more than 3,000 ­Russia-linked ads to congressional committees investigating the Kremlin’s influence operation during the 2016 presidential campaign.

The announcement that Facebook would share the ads with the Senate and House intelligence committees came after the social network spent two weeks on the defensive. The company faced calls for greater transparency about 470 Russia-linked accounts — in which fictional people posed as U.S. activists — which were taken down after they promoted inflammatory messages on divisive issues. Facebook angered congressional officials by showing only a sample of the ads, some of which attacked Hillary Clinton or praised President Donald Trump.

Facebook’s admission Sept. 6 that Russian agents covertly bought ads on the site during the 2016 campaign has brought intense scrutiny on the social network and on Twitter, entangling both companies in the investigation by Robert Mueller, the special counsel. Both companies have turned over detailed data to Mueller.

The disclosure of the ads also raised the possibility of regulation of political advertising on social media. This week, congressional Democrats asked the Federal Election Commission to advise on ways to prevent illicit foreign influence on American elections via social media, including possible new laws or regulations.

Facebook’s actions underscored how far it has strayed from being a mere technology company and how it is confronting the unintended consequences of the tools it provides to reach the more than 2 billion people who use the site regularly.

On Thursday, in a move clearly intended to pre-empt government intervention, Facebook’s chief executive, Mark Zuckerberg, outlined a list of actions Facebook planned to take in the coming weeks to make political advertising more transparent.

Twitter has announced that it will brief the Senate Intelligence Committee on Wednesday in private.

In a statement, Twitter did not address illicit Russian activity on its platform but said it “deeply respects the integrity of the election process, a cornerstone of all democracies” and vowed to “continue to strengthen our platform against bots and other forms of manipulation.”