WASHINGTON — Russian efforts to help elect President Donald Trump were intensely focused on exploiting racial tensions to suppress voter turnout among minorities, a campaign that proved more far-reaching and effective than previously understood, according to reports released Monday by the Senate Intelligence Committee.

More than 30 million Facebook and Instagram users shared propaganda messages generated as part of a campaign by Russia’s Internet Research Agency to polarize and misinform voters, according to the reports commissioned by the committee. The activities of Russian operatives and their crafting of messages in which they often posed as minority activists have been known for some time, but the new reports reveal extensive additional detail about how that operation spread such threads of misinformation far and wide.

“The most prolific IRA efforts on Facebook and Instagram specifically targeted Black American communities and appear to have been focused on developed Black audiences and recruiting Black Americans as assets,” said one of the reports, commissioned by the committee from the research firm New Knowledge. “The IRA exploited the trust of their page audiences to develop human assets, at least some of whom were not aware of the role they played. The tactic was substantially more pronounced on Black-targeted accounts.”

The release of the reports opens a new chapter into the probe on Capitol Hill into Russian election interference, sparking anger among Democrats and civil rights activists who note the Russian focus on alienating black voters ran parallel to Trump campaign efforts to do the same. The reports, while offering no evidence of collusion, give Democrats and federal prosecutors fresh fodder for their investigations into the possibility that the Russians and people close to Trump cooperated.

But the tactics are also consistent with a historic pattern in which Russian propagandists have used racial tensions in America to further their goals. In Soviet times, Russian agents worked diligently to fan the flames of racial discord in America.