The transition team in a statement Friday appeared to seek to raise doubts about the allegations of Russian interference by questioning the abilities of U.S. intelligence agencies.
The Washington Post and The New York Times in separate reports late Friday said the CIA presented evidence to some government officials that Russia sought to help Trump win.
U.S. officials familiar with the intelligence confirmed to ABC News that Russians hacked the computer systems of both Republicans and Democrats but leaked information only from Democrats’ accounts. However, intelligence officials told ABC News that the fact that only Democrats’ information was released isn’t enough to prove the motivations of the Russian actors.
One official told ABC News that in recent weeks U.S. intelligence uncovered information that "added a different layer" and "added clarity" to the government's understanding of Russia's role in hacking U.S. political institutions, but the official would not go so far as to say that Russia was motivated to get Trump elected.
Meanwhile, the Trump transition team's statement questioning the credibility of U.S. intelligence was deeply disturbing to many in the intelligence community, one official told ABC News. “That sent hard ripples across the intelligence community” and left many people angry, the official said.
“What proof does anyone have that they affected the outcome?” Spicer said a heated interview with CNN’s Michael Smerconish. “Zero. Show me what facts have actually shown that anything undermined that election.”
The reports in the Washington Post and New York Times appeared Friday after President Obama ordered a "full review" of Russian hacking related to the 2016 election and of any other election-related hacking going back to the 2008 election.
Rep. Eric Swalwell, D-California, a member of the House Intelligence Committee, called on Trump to take full advantage of the presidential daily briefings offered to him as the president elect in the wake of the reports.
"His perspective is not even an informed one - to draw that comparison without being fully informed," Swalwell said, referring to reports that Trump has been briefed only a handful of times since winning the election.
The White House and CIA declined to comment to ABC News.
Rep. Adam Schiff of California, the top Democrat on the House Intelligence Committee would not confirm the intelligence briefings reported by the Washington Post but called for a full congressional investigation. "One would also have to be willfully blind not to see that these Russian actions were uniformly damaging to Secretary Clinton and helpful to Donald Trump. I do not believe this was coincidental or unintended," he said in a statement.
Some Republican members of Congress also voiced concern about the reports of Russian hacking, which appeared to put them at odds with the president-elect's transition team on the issue.
“Don't have to be Sherlock Holmes to figure out what Russia is up to -- they're trying to undermine democracies all over the world,” tweeted Sen. Lindsay Graham of South Carolina. “I'm not challenging the outcome of the election, but very concerned about Russian interference/actions at home and throughout the world.”
Sen. John Cornyn of Texas tweeted that news of Russian hacking “has been going on for years. Serious, but hardly news.”
ABC News' Arlette Saenz and Mike Levine contributed to this report.