Michael Cohen began exchanging hundreds of phone calls and nearly 1,000 text messages with a US businessman related to a prominent Russian oligarch on the day Donald Trump won the 2016 election, a newly unsealed court filing said.

The businessman, Andrew Intrater, is the CEO of the US investment firm Columbus Nova.

Shortly after Trump's inauguration, Columbus Nova signed a $1 million consulting contract with Cohen, a deal that was under the scrutiny of federal investigators examined whether Cohen tried to sell access to the Trump White House.

The company also paid Cohen approximately $500,000 in consulting fees between January and August 2017.

paid Cohen approximately $500,000 in consulting fees between January and August 2017. Columbus Nova is an affiliate of the Russian energy conglomerate Renova Group. Intrater is also the cousin of the Russian oligarch Viktor Vekselberg, the head of Renova.

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Michael Cohen, President Donald Trump's longtime former lawyer and fixer, exchanged more than 230 phone calls and nearly 1,000 text messages with an American businessman tied to a prominent Russian oligarch after Trump won the 2016 US election.

The revelation was made in a search-and-seizure warrant against Cohen that was filed in August 2017 and unsealed on Wednesday. It was first reported by Bloomberg News.

"Telephone records related to Cohen's cellular telephone show that on or about Nov. 8, 2016, the day of the presidential election, a telephone registered to Cohen exchanged the first in a series of text messages with the CEO of Columbus Nova," the newly unsealed filing said.

The CEO, Andrew Intrater, is the cousin of Russian energy tycoon Viktor Vekselberg.

Intrater donated $250,000 to Trump's inaugural committee and is the head of the US investment firm Columbus Nova. The company paid Cohen approximately $500,000 in consulting fees between January and August 2017 and has been described in federal filings as an affiliate of Renova Group, a Russian conglomerate founded by Vekselberg.

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Cohen and Intrater "were working together so of course texted and called each other," Columbus Nova said in a statement to INSIDER. "This was all known and investigated, and wasn't even deemed worthy of being included in the special counsel's report."

Columbus Nova has sought to distance itself from Vekselberg and Renova Group since records of the payments to Cohen emerged last year. It has repeatedly denied that it is an arm of Renova Group.

But according to The Guardian, Columbus Nova has secured Vekselberg $450 million in loans from the Russian state-owned bank VTB Bank.

The New York Times also reported that Cohen also met with Vekselberg at Trump Tower eleven days before Trump's inauguration in January 2017. The purpose of the meeting was to discuss improving US-Russia relations under the Trump administration, Intrater told The Times.

Intrater told The Times that Vekselberg and Cohen met three times. The second time was during Trump's inauguration, which was attended by at least six Putin-allied Russians, including Vekselberg.

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Shortly after the inauguration, Columbus Nova signed a $1 million consulting contract with Cohen, a deal that was under the scrutiny of federal investigators.

Intrater told The Times last year that Vekselberg had not originally intended to meet with Cohen at Trump Tower, adding that if he had known Cohen would later be the focus of several federal criminal inquiries, he would not have hired Cohen or introduced him to Vekselberg.

Cohen is currently serving a three-year sentence in federal prison after pleading guilty to several crimes including lying to Congress, violating US election law, tax evasion, and bank fraud. He has accused the president and those around him for engaging in illegal conduct as well.

Most notably, Cohen told federal prosecutors that Trump was involved in campaign-finance violations related to payments made to two women during the 2016 election.

Read more: Michael Cohen implicated at least 4 people in Trump's orbit during marathon House testimony

He also testified that he believed Trump had advance knowledge of a June 2016 Trump Tower meeting between campaign officials and two Russian lobbyists, and he suggested Trump may have known ahead of time about WikiLeaks' plans to publish troves of hacked Democratic emails during the election.

This week, the House Intelligence Committee released two previously unseen transcripts of Cohen's testimony to the panel, which highlighted how legally treacherous to Trump's orbit Cohen is as a witness in the obstruction-of-justice investigation, too.

Cohen implicated at least four people close to the president in potential wrongdoing in his House testimony: Trump's defense lawyer Jay Sekulow; Trump's lead defense attorney, Rudy Giuliani; Trump's eldest son, Donald Trump Jr.; and an unnamed intermediary Cohen said is well-connected to the White House.