Former Trump national security adviser Michael Flynn is invoking his Fifth Amendment right against self-incrimination on Monday, refusing to hand over documents subpoenaed by the Senate Intelligence Committee.The panel wants to see documents relating to Flynn's interactions with Russian officials as part of its probe into Russia's meddling in the 2016 presidential election.In a letter to the committees chairmen, Flynn's attorney Robert Kelner writes "producing documents that fall within the subpoena's broad scope would be a testimonial act, insofar as it would confirm or deny the existence of such documents."The letter also states that Flynn is "the target on nearly a daily basis of outrageous allegations, often attributed to anonymous sources in Congress or elsewhere in the United States Government, which, however fanciful on their face and unsubstantiated by evidence, feed the escalating public frenzy against himFlynn was asked to resign in February from his post after it was revealed that he lied to Vice President Pence about his communication with Russia's ambassador to the U.S.The intelligence committee is one of multiple congressional panels that are looking into Flynn's conduct as well as possible collusion between the Trump campaign and Russia. Flynn has previously sought immunity from what he termed "unfair prosecution" so he could cooperate with the committee.In unclear exactly how the committee will respond to Flynn's refusal to hand over the documents. It could hold him in contempt of Congress, but Copyright 2017 NPR. To see more, visit http://www.npr.org/.