 -- President Trump's fired national security adviser, retired Army Lt. Gen. Michael Flynn, was paid a total of $56,200 in 2015 by three Russian firms owned by or closely tied to the Kremlin, new documents released by congressional Democrats appear to show.

The fees included $33,750 paid by Russia's state-owned TV network RT to the retired three-star general, who once served as director of the Defense Intelligence Agency, to speak at what the Russian organizers described to his speakers bureau as a "private, invitation-only conference." An additional $11,250 was paid to Leading Authorities, Flynn's speaking agents.

"General Flynn worked with a speakers bureau and what you're seeing is a result of that," said Flynn's spokesman, Price Floyd.

In the 24 pages of assorted 2015 emails and documents voluntarily handed over to the House Oversight Committee by Leading Authorities, RT did not mention that the Dec. 10, 2015 conference and dinner in Moscow celebrating the Russian network's 10th anniversary would be broadcast on television worldwide or that the star speaker -- within arm's reach of Flynn in a video of the televised event -- would be Russian President Vladimir Putin.

Floyd said he did not know if the retired general felt misled by RT in its correspondence before the 10th anniversary gala, which offered vague answers to speaker bureau questions about who else would attend. But he said Flynn informed defense intelligence officials both before and after the gala that he was attending as a paid guest.

"General Flynn informed and briefed DIA before his trip to Russia that he was going to get paid for it. On his return, he briefed DIA about his trip to Russia," Floyd said.

But Democrats claim the RT fee, as well as additional payments totaling $22,500 to Flynn by Russian cyber security firm Kaspersky Lab and Volga-Dnepr Airlines, add up to a clear violation of the Constitution's Emoluments Clause, which prohibits retired generals from accepting direct or indirect payments from foreign governments, according to the committee's ranking member Rep. Elijah Cummings (D-Md).

Cummings asked the Pentagon to investigate Flynn for this shortly before Trump fired him last month as White House national security adviser for not fully disclosing his discussions with Russia's ambassador to Washington during the transition.

In a new letter today, Cummings charged that Flynn had "violated the Constitution" by accepting such payments from "an agent of a global adversary that attacked our democracy," an apparent reference to U.S. intelligence agencies' assessment that Russian government-directed hackers had pilfered emails of the Democratic National Committee and Secretary Hillary Clinton's campaign manager John Podesta.

Pentagon officials, who have not said what if any actions would be taken by Secretary of Defense James Mattis, noted today that Cummings' latest letter was also addressed to Trump and referred ABC News to the White House. National Security Council officials there referred a reporter to Flynn's lawyers, who did not immediately return a call for comment.

Shortly after the Dec. 10, 2015 broadcast showing Flynn at the head table alongside CIA whistleblower Ray McGovern and Green Party presidential candidate Jill Stein, a senior U.S. intelligence official told ABC News it was a stunning image of the former military intelligence chief, "that close to a despot, an enemy to the U.S., at an event for the Russian government's propaganda arm."

On Nov. 24, 2015, Leading Authorities asked RT to provide Flynn with a list of who would be at his table with his son and "executive officer" at his private consulting firm, Flynn Intel Group, Michael G. Flynn. But RT replied only that invitees included "Russian politics leaders" and that the guest list was still being assembled.

On Dec. 1, 2015, an RT press release said that Flynn, former head of "the country’s main foreign military espionage organization," would appear at the gala dinner, as well as Stein and McGovern -- but RT did not announce that the keynote speaker was to be President Putin, the American nemesis and number one "Russian politics leader."

Flynn later acknowledged in press interviews the paid engagement to appear at the RT gala to talk about radical Islam, but he also has said he wasn't uncomfortable with it in hindsight, while declining to provide details about any payments from RT.

Because Flynn held a Top Secret/Sensitive Compartmented Information clearance, he also would have been required to report to the DIA any repeated contacts or payments from foreign nationals or foreign-owned firms as well as foreign travel, which Cummings also noted today in a request for more documents from the Trump administration.

Flynn began advising Trump on foreign policy matters in early 2016, according to published reports.

He was forced to leave his post as DIA director and retire as a three-star general officer in 2014 over his management style and clashes with the Obama administration over policy. Flynn had spent decades as an intelligence officer in the military and oversaw intelligence used to by the U.S. Joint Special Operations Command to kill Iraq's top insurgent leader, Abu Musab al-Zarqawi in 2006, who led the al-Qaeda branch that later became known as ISIS.

Congress is responsible for enforcing the emoluments clause and also has the power to exempt someone from it.

Documents recently filed by Flynn showed his consulting firm was paid more than $500,000 by a company tied to the government of Turkey for lobbying during the fall transition period, which critics say was ethically questionable.

EDITOR'S NOTE: The story has been updated to include new comments from Lt. Gen. Flynn's spokesman.