Social media website Facebook to provide the US Congress with over 3,000 adverts relating to the presidential election.
It says they appear to have come from accounts associated with a Russian entity, known as the Internet Research Agency.
US special counsel Robert Mueller is investigating alleged Russian interference in the 2016 US presidential election.
Moscow denies any meddling and US President Donald Trump has denied collusion by his campaign.
In a blog post, Facebook says: "We believe it is vitally important that government authorities have the information they need to deliver to the public a full assessment of what happened in the 2016 election.
"That is an assessment that can be made only by investigators with access to classified intelligence and information from all relevant companies and industries - and we want to do our part.
"Congress is best placed to use the information we and others provide to inform the public comprehensively and completely."
"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.
"Federal law also places strict limitations on the disclosure of account information."
Facebook CEO Mark Zuckerberg | Image: Facebook
The company adds: "At the same time, we will continue our own review and investigation, and to do our part to make sure investigators have the information they need.
Facebook CEO Mark Zuckerberg explains: "I spent a lot of time with our teams on the question of Russian interference in the US elections. I made some decisions on the next steps we're taking, and I want to share those with you now.
"I care deeply about the democratic process and protecting its integrity. Facebook's mission is all about giving people a voice and bringing people closer together. Those are deeply democratic values and we're proud of them.
"I don't want anyone to use our tools to undermine democracy. That's not what we stand for.
"The integrity of our elections is fundamental to democracy around the world."
"There will always be bad actors in the world, and we can't prevent all governments from all interference.
"But we can make it harder. We can make it a lot harder. And that's what we're going to do."
"While the amount of problematic content we've found so far remains relatively small, any attempted interference is a serious issue.
"We are actively working with the US Government on its ongoing investigations into Russian interference".