Lawyers for former National Security Adviser Michael Flynn said Monday he will not provide the Senate Intelligence Committee with documents requested under subpoena about Russian meddling in the 2016 election.

"The context in which the committee has called for General Flynn's testimonial production of documents makes clear that he has more than a reasonable apprehension that any testimony he provides could be used against him," the lawyers wrote in a letter to the heads of the committee informing them Flynn would invoke his Fifth Amendment right against self-incrimination.

"Multiple Members of Congress have demanded that he be investigated and even prosecuted. He is the target on nearly a daily basis of outrageous allegations, often attributed to anonymous sources in Congress or elsewhere in the United State Government," the letter states.

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Flynn's response, which was first reported by the Associated Press, noted that he is invoking his constitutional rights and it is not an admission of guilt. The committee, according to Flynn's lawyers, requested all records of his communications with President Donald Trump's campaign that were in any way related to Russia from the day Trump announced his candidacy in June 2015 through Inauguration Day.

Two other former associates of President Donald Trump -- Paul Manafort and Roger Stone -- complied with similar requests from the Senate panel, a congressional source told NBC News.

Flynn was fired in February after misleading Vice President Mike Pence and other senior White House officials about his communications with the Russian ambassador to the United States.

His relationship with officials in Moscow has been a focal point of the congressional investigations and Department of Justice probe into President Donald Trump's ties to Russia. Law enforcement officials told NBC News that Flynn and former Trump campaign manager Paul Manafort are key figures in the Russia investigation.

The investigation received renewed scrutiny after Trump fired FBI Director James Comey earlier this month, later telling NBC News' Lester Holt the ongoing probe played a role in his decision. Comey wrote a memo saying Trump asked him to shut down the investigation of Flynn, sources with knowledge of the document confirmed to NBC News.

The Senate Intelligence Committee turned down a request for immunity from Flynn's lawyer earlier this year. Monday's letter stated Flynn will comply with the congressional requests only with "assurances against unfair prosecution."

It is Mike Flynn's right to plead the 5th. We will get to the truth one way or another. We need facts, not speculation & anonymous sources. — Sen. James Lankford (@SenatorLankford) May 22, 2017

There are three methods Congress can respond to someone not complying with a subpoena, according to a recent report from the Congressional Research Service. They can detain an individual until he or she complies with the Congressional request, they can pursue a criminal prosecution through the executive branch, or rely on the judicial branch to enforce the subpoena.