WASHINGTON (BLOOMBERG) - Facebook told a US Senate panel that it has detected "only what appears to be insignificant overlap" between targeting of ads and content promoted by a pro-Kremlin Russia group and by the presidential campaign of Donald Trump.

The social-media company said it "does not believe it is in a position to substantiate or disprove allegations of possible collusion" between Russia and the Trump campaign, as part of a written response to questions from the Senate Intelligence Committee released on Thursday evening (Jan 25) by the panel. Facebook didn't go into further detail, saying it was willing to schedule a meeting with Senate staff to discuss the matter.

The remarks go beyond what the company told Congress during public hearings on Nov 1 as part of probes into Russian election meddling. At that time, Facebook General Counsel Colin Stretch said, "We have not seen overlap in the targeting - that was relatively rudimentary - used in the advertising that was disclosed, and any other advertiser on the site, including the Trump campaign."

In responding to the Senate panel, Facebook, Twitter and Alphabet's Google defended their efforts to combat malicious content on their networks and touted new disclosure efforts for election-related content that should be up and running for the 2018 mid-term elections.

The company answers aren't likely to quell concerns from lawmakers that the companies might not have found all of the abuse of its networks by Russians or taken enough steps to prevent future actions.

Facebook said it has no evidence that the Russian Internet Research Agency, which disseminated fake news and ads, targeted its efforts based on US voter registration data. Their targeting was "relatively rudimentary, targeting broad locations and interests," the company said. Any revenue that Facebook made from ads run by the IRA was "immaterial", it added, noting that it was contributing hundreds of thousands of dollars to the Defending Digital Democracy Project.

Facebook also said that the IRA organised 129 real-world events, viewed by approximately 338,300 people, with 62,500 people saying they were planning to attend. Facebook said that in some cases, its algorithm did automatically recommend that people view, follow or join Russian-linked pages, because the company wasn't aware that they were not legitimate.

Twitter and Google didn't address the possibility of overlap between the Russian-backed IRA and the Trump campaign in their latest answers.

But Twitter did say it wasn't aware of "any specific state-sponsored attempts to interfere in any American elections in 2017, including the Virginia and New Jersey gubernatorial elections". Twitter said it was unable to monitor every tweet posted in relation to real-time events, but that it dedicated nearly the entire engineering, product and design teams to address malicious automation, bots and other coordinated activities in the beginning of 2017.

Its automated systems are supplemented by internal, manual reviews conducted by Twitter employees, the company said. "We are committed to addressing the spread of misinformation on our platform - and to prevent future attempts to interfere with US elections - but we recognise that spam and malicious automation are not limited to political content and can undermine the positive user experience we seek to offer irrespective of the content," the company said.

Google told Senate investigators it is working on "greater transparency" for news in its search results, including labelling sources that receive funding from governments. RT and Sputnik, prominent publishers backed by the Russian government, are now labelled in searches, the company said. Google also said it's planning to apply the same disclosures on YouTube, its massive video site, although it didn't offer specifics.

In response to a question from Republican Senator Tom Cotton, Twitter defended hosting accounts from Wikileaks and its founder Julian Assange, as well as former National Security Agency contractor Edward Snowden, who stole and released a trove of highly classified data. "Consistent with our values and commitment to fostering an open exchange of ideas, unless the activity or posted content violates our Terms of Service or Twitter Rules, we do not bar controversial figures from our platform or prohibit accounts from posting controversial content," the company said.