House Intelligence Committee Chairman Devin Nunes, R-Calif., speaks to reporters on Capitol Hill in Washington, Friday, March 24, 2017. AP Photo/J. Scott Applewhite A bipartisan group of lawmakers and aides have viewed classified reports that House Intelligence Committee chairman Devin Nunes said showed evidence that some Trump associates were caught up in federal surveillance activities during the 2016 election.

The documents seen by lawmakers at the National Security Agency's headquarters show no evidence that President Barack Obama's national security adviser, Susan Rice, acted illegally by requesting that the names of some US citizens be unmasked during investigations into Russia's alleged involvement in the US election, CNN reported on Tuesday.

Trump had called the unmasking — an action by which a US citizen's identity is revealed in the course of routine federal surveillance — "one of the big stories of our time" in a New York Times interview last week.

Nunes stunned colleagues on the bipartisan House Intelligence Committee last month when he held a press conference announcing he had seen documents that showed "incidental collection" of information on some members of Trump's campaign team.

The bombshell revelation was seen by Trump and some of his supporters as vindication for the president's baseless claims that Obama ordered a spying operation on his campaign during the election.

CNN's report, which cited multiple unnamed Democratic and Republican sources, said Rice's unmasking requests were nothing out of the ordinary. Rice said the same in an interview on MSNBC last week, adding that any suggestion that her actions were politically motivated were "absolutely false."

Nunes has since stepped aside from the House Intelligence Committee's Russia investigation.