Russia hacked into Republican state political campaigns and old email domains of the Republican National Committee but there is no evidence it successfully penetrated President-elect Donald Trump's campaign, FBI Director James Comey said on Tuesday.

Comey also told lawmakers Russia did not release information obtained from the state campaigns or the old RNC email domains, comments that may buttress the U.S. intelligence view that Moscow tried to help Trump against Democrat Hillary Clinton in the 2016 campaign.

U.S. intelligence agencies on Friday released an assessment that Russian President Vladimir Putin ordered a covert effort to help Republican Trump's electoral chances by discrediting Clinton.

The report, which omitted classified details, was the U.S. government's starkest public description of what it says was a Russian effort to manipulate the American electoral process by leaking hacked emails from Democrats.

Russia has denied interfering in the election but President Barack Obama expelled 35 Russian suspected spies from the United States and imposed sanctions on two Russian intelligence agencies last month in response to the allegations. Defense Secretary Ash Carter told a news conference on Tuesday those penalties were "a start and not the end" of U.S. retaliation for the hacks, and senior officials have suggested covert action may be taken.

Comey told lawmakers the Federal Bureau of Investigation "did not develop any evidence that the Trump campaign, or the current RNC, was successfully hacked." He did not say whether Russia had tried to hack Trump's campaign.

Trump has disputed the accusations of Russian cyber attacks during the election, but his incoming chief of staff said on Sunday that the New York businessman accepts the U.S. intelligence community's conclusions that Russia was responsible, and that further action may be taken against Moscow.

SENATE HEARING

Comey declined to comment on whether or not the FBI might be investigating links between Russia and associates of Trump, who frequently called during the campaign for improved relations between Washington and Moscow.

The FBI director was pressed by Senator Ron Wyden, an Oregon Democrat, to publicly provide a declassified answer to the question before Jan. 20, the day Trump will be inaugurated, but Comey suggested he would unable to do so.

Comey appeared before the Senate Intelligence Committee along with the director of national intelligence, the head of the Central Intelligence Agency and the chief of the National Security Agency at a time of controversy in Washington about the 2016 election.

Testifying before Congress for the first time since Trump beat Clinton on Nov. 8, Comey has been criticized by Democrats for statements about a separate investigation into Clinton's use of a private email server as secretary of state.

The controversy over Russia's alleged role in attempting to influence the election has roiled Washington, with Democratic lawmakers calling for an independent commission to investigate the matter and Republicans worried that the affair might call into question the legitimacy of Trump's victory.

Comey said there was evidence Russia hacked Republican state-level political campaigns and "old" email domains that the RNC was no longer using.

In contrast, Friday's report assessed that Russian military intelligence used intermediaries such as WikiLeaks, DCLeaks.com and the Guccifer 2.0 "persona" to release emails that it had acquired from the Democratic National Committee and top Democrats as part of the effort to help Trump and harm Clinton.

The DNC denied "multiple requests" made by the FBI to examine its hacked servers, Comey said. He added that his agents relied on a forensic analysis conducted by the cyber security firm CrowdStrike, which was hired by the DNC to help clean up the hack when it was detected last spring.

Senior U.S. Republican and Democratic senators introduced legislation on Tuesday seeking to impose a wide range of sanctions on Russia over its cyber activities and actions in Syria and Ukraine.