Nunes however said there was no evidence that then-president Barack Obama ordered the surveillance -- as Trump has claimed -- or that the president was the target.
Rather, Nunes suggested, Trump's communications were picked up during court-approved targeting of suspected foreign intelligence operatives.
The communications were not linked to Russia, he said, adding that they appeared to have "little or no intelligence value."
"The president himself and others in the Trump transition team were clearly put into intelligence reports," Nunes told reporters in front of the White House after briefing the billionaire president on the situation.
The information collected, spanning the November-January period between Trump's election victory and his inauguration, was "widely disseminated" in US intelligence circles, he said.
US intelligence community rules dictate that information on US citizens picked up incidentally in surveillance must be scrubbed or masked in intelligence reports.
Nunes suggested those involved in the surveillance had violated those rules.
As for Trump, he indicated he felt vindicated by the revelation.
"I somewhat do. I must tell you I somewhat do," he said during a White House meeting.
"I very much appreciated the fact that they found what they found. I somewhat do."
On March 4, Trump implied his predecessor had broken the law in targeting him.
"Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism!" he tweeted.
Nunes' revelation threatened to upend a bipartisan investigation into alleged Russian interference in the November election and Moscow's possible collusion with the Trump campaign.
Adam Schiff, the ranking Democrat on Nunes' committee, voiced anger that the Republican had taken the information to the president -- and the media -- before the committee had been consulted.
The chairman, he said, "shared this information with the White House before providing it to the committee, another profound irregularity," he said.
"I have expressed my grave concerns with the chairman that a credible investigation cannot be conducted this way."
Schiff added "it certainly does not suggest -- in any way -- that the president was wiretapped by his predecessor."
Bradley Moss, a leading national security lawyer, told AFP that Nunes could be in trouble because he "released what appears to be classified information."
"Disclosure of the fact that an individual's communications were collected, even incidentally... is a closely held classified fact. You can't just go around spilling that information," he said.
The lawmaker's statement came amid recriminations over spy agencies listening to phone calls between former Trump national security advisor Michael Flynn and Moscow's ambassador in Washington, which has become part of a sprawling probe into Russia's role in the US election.
It also came days after the heads of the National Security Agency and the Federal Bureau of Investigation repudiated Trump's claims that his Trump Tower in New York had been wiretapped under order by Obama.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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