WASHINGTON — Russian agents intending to sow discord among American citizens disseminated inflammatory posts that reached 126 million users on Facebook, published more than 131,000 messages on Twitter and uploaded over 1,000 videos to Google’s YouTube service, according to copies of prepared remarks from the companies that were obtained by The New York Times.

The detailed disclosures, sent to Congress on Monday by companies whose products are among the most widely used on the internet, came before a series of congressional hearings this week into how third parties used social networks and online services to influence millions of Americans before the 2016 presidential election.

The new information goes far beyond what the companies have revealed in the past and underline the breadth of the Kremlin’s efforts to lever open divisions in the United States using American technology platforms, especially Facebook. Multiple investigations of Russian meddling have loomed over the first 10 months of the Trump presidency, with one leading to the indictments of Paul Manafort, the former Trump campaign chief, and others on Monday.

In its prepared remarks sent to Congress, Facebook said the Internet Research Agency, a shadowy Russian company linked to the Kremlin, had posted roughly 80,000 pieces of divisive content that was shown to about 29 million people between January 2015 and August 2017. Those posts were then liked, shared and followed by others, spreading the messages to tens of millions more people. Facebook also said it had found and deleted more than 170 accounts on its photo-sharing app Instagram; those accounts had posted about 120,000 pieces of Russia-linked content.