Facebook has said it will share with US authorities political ads that it says Russia-based operatives ran on the social network around the time of last year's US presidential election.
The company said it is launching an overhaul of how it handles paid political advertisements on the world's largest social network.
Facebook has been criticised that it has not done enough to prevent the manipulation of elections.
Chief Executive Mark Zuckerberg said the company would start by sharing with US congressional investigators some 3,000 political ads that it said Russia-based operatives ran on Facebook in the months before and after last year's US presidential election.
Donald Trump, the victor in that election, has tweeted this morning that the "Russian hoax continues, now it's ads on Facebook" following the announcement.
The Russia hoax continues, now it's ads on Facebook. What about the totally biased and dishonest Media coverage in favor of Crooked Hillary?— Donald J. Trump (@realDonaldTrump) September 22, 2017
The greatest influence over our election was the Fake News Media "screaming" for Crooked Hillary Clinton. Next, she was a bad candidate!— Donald J. Trump (@realDonaldTrump) September 22, 2017
Earlier this month, Facebook said an operation likely based in Russia spent $100,000 on thousands of Facebook ads promoting divisive messages.
US congressional investigators and Special Counsel Robert Mueller are examining alleged Russian election interference which Moscow has denied.
Mr Zuckerberg, who has remained largely silent on the subject for months, pledged in a live broadcast on Facebook to make political advertising more transparent on his network in future.
"We will work with others to create a new standard for transparency for online political ads," he said.
He said political advertising will now carry disclaimers about which campaign or organisation paid for it.