Post-election communications of Donald Trump’s team were swept up in an “incidental collection” by intelligence agencies, a Republican lawmaker says.
House intelligence committee chairman Devin Nunes said individuals were named in “widely disseminated” reports, which he said was “totally inappropriate”.
Mr Nunes said this was not evidence to back Mr Trump’s claim that Barack Obama had ordered wiretapping of Trump Tower.
But when asked if he felt vindicated, Mr Trump said: “I somewhat do.”
Mr Nunes also insisted the collected information was not linked to an FBI investigation into alleged links between the Trump team and Russian officials during the election campaign.
He said the incidental collection was apparently legal but “I don’t know if it’s right”, adding that some of the information he had seen “seems to be inappropriate”.
Such gathering of intelligence is usually related to communications US individuals have with foreign powers.
But American citizens involved in such incidental information are usually unidentified.
Analysis: BBC North America correspondent Anthony Zurcher
US intelligence agencies regularly monitor foreign individuals of interest, so if a member of the Trump transition team – or Donald Trump himself – communicated with a person under surveillance, it’s likely those interactions would be recorded.
That would constitute “incidental”, legal surveillance as described by Devin Nunes in his press conference on Wednesday afternoon. What that means, however, is open to interpretation.
Trump supporters may point to this “startling revelation”, in press secretary Sean Spicer’s words, as evidence that the president correctly suspected his communications were being intercepted. They will also probably question who “unmasked” the names of Trump advisers, when the default is to avoid revealing the identities of US citizens communicating with monitored foreign nationals.
Mr Trump’s critics are sure to wonder what kind of interactions the Trump team was having with individuals worthy of US intelligence surveillance. Were these communications authorised, and what topics did they cover? It was just such intelligence intercepts that revealed that former National Security Adviser Michael Flynn had been lying about the nature of his phone discussions with Russian Ambassador Sergey Kislyak, after all.
This story is like a spinning top, impossible to know which way it will next turn.
Mr Nunes’s main concern was that people involved had been unmasked in the reports.
He said: “Details about US persons involved in the incoming administration with little or no apparent foreign intelligence value were widely disseminated in intelligence community reports.”
Mr Nunes said President Trump was “concerned” when he briefed him at the White House, and it was “possible” Mr Trump’s own communications were collected.
He said the intelligence collection was brought to his attention, also legally, by an unnamed source or sources.
He said the collection took place mainly in November, December and January.
Mr Trump was later asked if he felt vindicated, and answered: “I somewhat do. I very much appreciated the fact that they found what they found.”
White House press secretary Sean Spicer said this was a “startling revelation” and that there were “a lot of questions that need to get asked; how many times was one individual followed? Did their names get unmasked and why?”
Trump campaign advisers are currently the subject of an FBI investigation and two congressional inquiries.
Investigators are reviewing whether the Trump campaign and its associates co-ordinated with Moscow to interfere in the 2016 presidential election campaign to damage Mr Trump’s opponent, Hillary Clinton.
Trump team ‘incidentally monitored’ after election