Facebook has said it will release more than 3,000 ads thought to have been bought by Russian agencies during the US election.
The company, which has come under pressure from US politicians to reveal the ads, said after an "extensive legal and policy review", it had decided to comply with requests.
"This has been a difficult decision. Disclosing content is not something we do lightly under any circumstances. We are deeply committed to safeguarding user content, regardless of the user’s nationality, and ads are user content," said Facebook in a statement.
But it added the 3,000 ads, which ran between 2015 and 2017 and addressed "political and social issues", had been bought by accounts associated with Russia's Internet Research Agency.
"We subsequently made clear that we are providing information related to those ads, including the ad content itself, to the Special Counsel investigating allegations of Russian interference in the 2016 US election," it said.
"Today we are announcing that we will also share these ads with congressional investigators."
The move is thought to be a response to pressure from lawmakers on both sides of the political divide, who have accused it of holding back.
Earlier this month Facebook estimated that between June 2015 and May this year, the agency spent $100,000 on ads which focused on amplifying divisive social and political messages across the ideological spectrum, targeting subjects including race issues, immigration and gun rights.
Earlier this year a report by US intelligence agencies said the Russian government had helped Donald Trump win the election.
"We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the US presidential election," it said.
"We further assess Putin and the Russian government developed a clear preference for President-elect Trump. We have high confidence in these judgments."