(Reuters/Dado Ruvic)

Russian operatives used Facebook to publicize 129 phony event announcements during the 2016 presidential campaign, drawing the attention of nearly 340,000 users -- many of whom said they were planning to attend -- according to a company document released by the Senate Intelligence Committee Thursday.

It's not possible to know how often people gathered in response to the sham announcements, but the numbers highlight how Russian operatives were successful in prompting Americans to express a willingness to act. In some cases, Russians allegedly working in an office building in St. Petersburg motivated at least some people to mobilize behind various causes, a striking accomplishment for a foreign influence campaign.

“Not only did they influence how people viewed Russian policy, they got people to take physical action. That’s unprecedented,” said Clinton Watts, a former FBI agent who studies Russian disinformation for the Foreign Policy Research Institute. “They just did it persistently, and they did it well.”

Facebook gives groups the ability to announce events and solicit interest from users, who can register their intention to attend. Facebook, which along with other big tech giants sought to downplay the Russian activity for months, declined to disclose a list of the 129 events publicized by the operatives. The company has said the operatives were linked to the Internet Research Agency, often called a "troll farm" because it employs people who use fake accounts to intentionally manipulate online conversations.

Previous disclosures by Facebook make clear that the operatives focused their disinformation campaigns on sensitive social issues, including racial and religious controversies, gun rights, police violence, southern heritage and immigration.

Facebook had previously disclosed details about a particular event advertised by Russian-controlled accounts. A group called Heart of Texas, announced a rally to take place May 21, 2016, under the banner of “Stop Islamization of Texas.” A separate Russian-controlled group, United Muslims of America, publicized a competing rally to “Save Islamic Knowledge” at the same place and time, prompting two groups to face off in competing demonstrations in Houston — a sign of how Russians hoped to turn divisions into open conflict.

The document, which includes written responses by Facebook to questions posed by members of the Senate Intelligence Committee, contains several revelations, including that there was some "overlap" between targeting of voters by Russian accounts and the campaign of Donald Trump. Facebook called this overlap "insignificant" in the document -- echoing remarks made in a Nov. 1 hearing by the company's general counsel Colin Stretch.

Facebook in its written response did not directly answer a question about whether it has found evidence that Russians sought to meddle last year's state elections in Virginia and New Jersey. But a spokesman said Thursday night that the company has not yet seen any sign of Russian influence during those campaigns.

The revelation about the events publicized on Facebook came in response to a question by Sen. Kamala  Harris (D-Calif.) about the subject. The company wrote in the document released Thursday that, "a total of 129 events were created across 13 IRA Pages. Approximately 338,300 unique accounts viewed these events. About 25,800 accounts marked that they were interested in an event, and about 62,500 marked that they were going to an event. We do not have data about the realization of these events."

Facebook has generally been more aggressive than other technology companies identifying and publicly explaining the Russian manipulation on its platform during the 2016 election and its aftermath, but it has drawn criticism for moving slowly to detail how much disinformation spread on its platform and how many people it reached. The company told lawmakers shortly before the November hearing that 126 million people saw free posts made by 470 Russian accounts and pages affiliated with the Internet Research Agency, and 10 million saw ads paid for by these accounts and pages.

Yet even with those numbers public for months, researchers were struck by the large number of events that Russian-linked accounts announced and the apparent appeal to American voters.

"This shows the effort to create long-term relationships with segments of the American public," said Jonathan Albright,  research director at the Tow Center for Digital Journalism at Columbia University. "This was also about measuring individual motivations to translate online signals into real-world behaviors."

The Senate committee also released responses from Twitter and Google.

In one case, lawmakers asked Twitter why a Russian-linked account called Guccifer2.0 was allowed to stay active after tweeting material hacked from the Democratic National Committee. The company responded that it could not comment on matters that may be related to specific law enforcement investigations.

Google described the difficulty of distinguishing content from Russian operatives and American political activists. "Many times,” Google wrote, "the misleading content looks identical to content uploaded by genuine activists. We are dealing with difficult questions that require the balancing of free expression, access to information, and the need to provide high quality content to our users.