When longtime Baltimore activists first saw a Facebook account called “Blacktivist” organizing a local police brutality march, they were immediately suspicious. The page honoring Freddie Gray, who had died in police custody a year earlier, quickly acquired a sizable following, but no one knew who was running it.

Heber Brown III, a pastor and community organizer, messaged Blacktivist asking if the person lived in Baltimore.

“No,” replied Blacktivist on 15 April 2016. “But there are people in Baltimore. Volunteers. We are looking for friendship, because we are fighting for the same reasons.”

At the time, Brown thought it was an out-of-town figure trying to co-opt the local movement for publicity. Another activist, Jamye Wooten, theorized Blacktivist could be an undercover police officer spying on protesters.

Neither thought the online figure purporting to be an ally was an agent of Russia.

The Blacktivist account now appears to have been part of the Kremlin’s covert efforts to stoke racial tensions and influence the US election, according to CNN, which cited sources with knowledge of the matter.

The report is an intriguing twist to the controversy embroiling Facebook and Twitter, which are facing growing scrutiny in Congress amid concern that false news stories, fake profiles and automated Russian bots spread on their platforms.

However, the proactive role Blacktivist played in communicating with activists, with authentic-seeming turns of phrase, suggests another level of sophistication.

For example, when Brown, in a private message thread with Blacktivist, criticized the impostor for organizing a Baltimore event, the account responded with a sincere-sounding apology: “What can we do to make the situation better now.” A minute later, the apparently contrite Blacktivist added: “I got you. This must be really wrong. I feel ashamed.”

Brown publicly urged his followers not to attend Blacktivist’s march, and it’s unclear what kind of effect the propaganda had in Baltimore.

However, archived posts from the since-deleted Blacktivist pages – which reportedly had 360,000 likes on Facebook, surpassing an official Black Lives Matter account – show its commentary emulated and contributed to the outrage fueling the movement.

“COPS RAID WRONG HOME AND ASSAULTED PREGNANT WOMAN,” the account said in one Facebook post, linking to a story of police violence. “INSANE! COPS PULVERIZED HANDCUFFED MAN” said another. Other Blacktivist posts urged followers to “stand together and end oppression”, saying, “Our race is under attack, but remember, we are strong in numbers”.

The message appears to have fooled bona fide activists, and promoted legitimate Black Lives Matter protests, supporting the notion that cheap social media propaganda can have a significant impact.

Wooten, an activist with Baltimore United for Change who also exchanged messages with Blacktivist, said the account, which used Freddie Gray as a profile photo before approaching activists online, “did a good job of creating an online narrative”.

He said the experience was a reminder that activists need to be cautious and consider “who is behind these online organizations before we start following and retweeting”.

Neither social media company responded to requests for comment on the reports that Russia was behind their Blacktivist accounts. But the report has left many prominent Black Lives Matter activists baffled and frustrated.

“I thought it was just another person who wanted to take advantage of the misery and pain of black people in Baltimore,” said Brown, 37, recounting his communication with Blacktivist. “We are just sick of people – anybody, conservatives and liberals – using black people’s pain as a football to advance other agendas.”

If the Blacktivist account is linked to Moscow, it will lend further credence to the findings of US intelligence officials that Russia was involved in influencing US politics. Facebook recently admitted that a Russian influence operation had purchased $100,000 worth of ads to spread divisive political messages, and the company has since agreed to provide 3,000 ads to Congress.

However, the connection to Black Lives Matter – a movement born out of police violence against black Americans that did not, itself, have a divisive role in the US presidential election – raises questions about the motives behind the Kremlin’s interference.

Experts in Russian history and US civil rights said that while the Blacktivist accounts may not have been directly linked to the US election, they are consistent with what would be expected from a propaganda campaign directed from Moscow intended to foment division.

“This is not because the Russians are believers in the ideologies espoused by any of these movements,” said Mark Jacobson, a Georgetown University professor who recently released a report on Russian influence operations. “This is about the Russians exacerbating pre-existing tensions. By building upon these existing divides.”

Antonio French, a prominent activist and Black Lives Matter supporter in Ferguson, Missouri, where Russia reportedly targeted at least one of its Facebook ads, said he was particularly concerned about the way social media enabled propagandists to engage in “micro targeting” of specific groups.

“I found it very disturbing that there was this orchestrated, well-funded attempt to exploit our divisions,” he said. He added it would be “interesting” when investigators and historians look back to “figure out how much of today’s divisions came naturally versus how much of it has been fueled by people whose sole purpose is to divide us”.

Dov Levin, a postdoctoral fellow at Carnegie-Mellon University who has studied Russian intervention in elections, noted that US officials were concerned that the Soviet Union was damaging America’s reputation around the world with propaganda seeking to inflame the civil rights movement in the 1960s.

“We know that the US government was extremely worried that this type of message was effective,” he said. Jacobson also noted that Soviet intelligence sought to discredit Martin Luther King Jr and promote more militant activist groups in hopes of provoking a full-blown “race war”.

“They want to see people rioting in the streets,” he said.

Levin speculated that one of the goals of a Russian Black Lives Matter campaign could have been to promote overall distrust in the political system with the hope of depressing black voters’ turnout.

For some activists used to dealing with outside forces surveilling or infiltrating social movements, the intense focus and outrage about Russia has been frustrating – especially when, they believe, US politicians continue to ignore systemic racism.

“Our biggest concern is our local government, how black lives are being treated in America, not so much Russia’s possible interference,” said Wooten. “That’s not anywhere near the top of our list of concerns.”