WASHINGTON (Reuters) - The Republican chairman of the U.S. House of Representatives intelligence committee set off a political firestorm on Wednesday when he said the communications of members of Donald Trump’s transition team were caught up in incidental surveillance targeting foreigners. Representative Devin Nunes said at a news conference that it was possible President Trump’s own communications were also intercepted and disseminated among U.S. intelligence agencies. The White House seized on Nunes’ remarks, which had cited anonymous sources, to bolster Trump’s unproven assertion that former President Barack Obama’s administration spied on the incoming president. Nunes himself said there is no proof of that, as have other lawmakers of both parties and the FBI director. A short while later, Trump spokesman Sean Spicer cited Nunes’ comments at his White House news briefing. “I do think it is a startling revelation, and there’s a lot of questions that need to get asked,” Spicer said. Democrats denounced Nunes’ statements as highly unusual from the chairman of an intelligence committee, with the top Democrat on the committee saying its members had not been informed and implying that Nunes was giving political cover to the president. Intelligence reports about the communications appeared to “unmask” the identity of the Trump associates and the names were widely shared among the agencies, Nunes said. He said it was possible Trump’s own communications were also collected. The National Security Agency routinely collects electronic communications on foreigners through a variety of surveillance tools. But information about Americans is also sometimes incidentally gathered, such as when someone is communicating to a foreign target.  Typically the names of Americans are made anonymous, or masked, in foreign intelligence reports unless an intelligence agency determines the identity of that person is relevant to national security or a criminal investigation. It was unclear why the reports Nunes cited contained unmasked names. A U.S. government source said it was logical, if not normal, that communications from Trump aides would have been incidentally intercepted by U.S. agencies after his election, given that they would have an interest in talking to foreign governments. Trump took office on Jan. 20. Two days ago, the director of the Federal Bureau of Investigation, James Comey, told a hearing of Nunes’ committee that his agency was conducting a criminal investigation of potential links between Trump associates and Russia’s attempts to influence the 2016 U.S. election to benefit Trump. “I recently confirmed that on numerous occasions the intelligence community ... collected information about U.S. citizens involved in the Trump transition,” said Nunes, who was himself on Trump’s transition team. Nunes said he was referring to intelligence reports of communications collected under the Foreign Intelligence Surveillance Act. “I want to be clear, none of this surveillance was related to Russia or the investigation of Russian activities or of the Trump team,” he said. Trump said he felt “somewhat” vindicated by Nunes’ announcement after being briefed by Nunes. FBI head Comey on Monday said that Trump’s claims were groundless. According to Nunes, the conversations in question were collected legally in November, December and January. In an interview with CNN, the committee’s leading Democrat, Adam Schiff said, “The chairman will need to decide whether he is the chairman of an independent investigation into conduct which includes allegations of potential coordination between the Trump campaign and the Russians, or he’s going to act as a surrogate of the White House, because he cannot do both.” Nunes’ remarks appeared tied to a line of questioning from Republicans during Monday’s hearing about the importance of identifying and prosecuting those responsible for intelligence leaks. Republicans have focused much of their discussion of the issue on the release of the names, or “unmasking” of Trump associates in the investigation. Trump fired his former national security adviser, General Mike Flynn, after the revelation that he had spoken to Russian Ambassador Sergei Kislyak, during the transition - which was leaked to the press after those calls were caught by surveillance intercepts. Nunes appeared to suggest intelligence reports about intercepts other than Flynn’s conversations existed.     Former intelligence officials and Democrats said Nunes’ announcement was highly unusual from the chairman of an intelligence committee. Schiff said he was not consulted by Nunes before his news conference. Nunes’ decision to share the information with the White House before informing the committee was a “profound irregularity,” Schiff said, adding that “a credible investigation cannot be conducted this way.” Schiff said the unmasking of a U.S. person may be appropriate in the context of an investigation. U.S. intelligence agencies have accused Russia of seeking to influence the presidential election in Trump’s favor against Democratic candidate Hillary Clinton by hacking computer systems and spreading disinformation. Russia denies the allegations. Nunes said he was “very concerned” about whether U.S. intelligence agencies were spying on Trump. He briefed Republican House Speaker Paul Ryan before the news conference and went to the White House to share the information. Admiral Mike Rogers, the director of the National Security Agency, was asked by Republicans at Monday’s hearing about the agency’s policies for “unmasking” the names of Americans whose communications were incidentally collected under foreign surveillance programs. Rogers said that 20 NSA employees, including himself, have the authority to unmask the identity of an American’s communications, and that senior officials at the CIA, FBI and Justice Department can make such a request. Asked how many Americans had been unmasked since June 2016, Rogers said he did not know. 