As WikiLeaks continues to publish emails belonging to Clinton campaign chair John Podesta, US officials told CNN that there is growing evidence that Russia is using the organization as a delivery vehicle for the messages and other stolen information.
The methods of the disclosures "suggest Moscow is at least providing the information or is possibly directly responsible for the leaks," one US official said.
US intelligence officials are still investigating the degree of connection between Russia and WikiLeaks but they remain confident that Russia is behind the leaks themselves.
CNN attempted to reach WikiLeaks for comment but received no response. WikiLeaks's founder, Julian Assange, has previously denied any connection to or cooperation with Russia.
On Friday, former Acting CIA Director Mike Morrell said on a conference call organized by the Clinton campaign that it was "absolutely clear ... WikiLeaks and Guccifer 2 are working with the Russians on this."
Russia's highest officials are dismissing accusations that Moscow is trying to sway the US presidential election with cyber attacks, speaking out before the latest accusation concerning WikiLeaks was shared with CNN on Thursday.
President Vladimir Putin ridiculed such talk Wednesday as "hysteria."
"Let them prove it," Sergei Lavrov told CNN's Christiane Amanpour
, waving off a US vow to retaliate with a "proportional response."
"If they decided to do something, let them do it," Lavrov told Amanpour. "But to say that Russia is interfering in the United States domestic matters is ridiculous."
The Director of National Intelligence -- representing 19 US intelligence agencies -- and the Department of Homeland Security leveled unambiguous charges against Russia on Friday. And the comments from Moscow did little to quell the growing criticism of Russia Wednesday from the Obama administration and Hillary Clinton's campaign.
"The kinds of disclosures that we've seen, including at WikiLeaks, of stolen e-mails from people who play an important role in our political process is consistent with Russian- directed efforts," White House Press Secretary Josh Earnest said Wednesday.
Podesta, whose emails are being published by WikiLeaks, also pointed the finger at Russia.
'Work of the Russian government'
"It is now clear that the illegal hack of my personal email account was -- just like the other recent, election-related hacks -- the work of the Russian government," Podesta said in a statement. "This level of meddling by a foreign power can only be aimed at boosting Donald Trump and should send chills down the spine of all Americans, regardless of political party."
Podesta earlier accused Roger Stone, a long-time adviser to Republican nominee Donald Trump, of having advance knowledge of the recent hack and publication of his emails on the website WikiLeaks, founded by Julian Assange. Stone had penned a tweet in August saying, "Trust me, it will soon (be) the Podesta's time in the barrel.
"I think it's a reasonable assumption to -- or at least a reasonable conclusion -- that Mr. Stone had advanced warning and the Trump campaign had advanced warning about what Assange was going to do," Podesta told reporters Tuesday.
But Stone rejected Podesta's assertion, telling CNN he "had no foreknowledge" of the WikiLeaks publication of Podesta's emails.
The accusations and denials are just the latest and perhaps most extraordinary way that Russia has become a factor in the wildly unpredictable 2016 presidential campaign. Ongoing questions about Trump's ties to Russia are now interspersed with Democratic accusations that Russia is actively trying to help the New York real-estate mogul reach the White House.
"We have never in the history of our country been in a situation where an adversary, a foreign power, is working so hard to influence the outcome of the election," Clinton said at the second presidential debate on Sunday. "And believe me, they're not doing it to get me elected. They're doing it to try to influence the election for Donald Trump."
Trump batted back the accusations at a rally in Ocala, Florida, Wednesday.
"Anything that goes wrong they blame Russia," Trump told the crowd. "We are being hacked because we have people who don't know what they are doing. They always blame Russia."
"They say Donald Trump is friends with Putin. I don't know Putin, folks," Trump added. "What the hell do I have to do with Putin?"
Trump and Putin
At a time when US-Russia relations are the worst they've been in decades, that question -- what does Trump have to do with Putin? -- still lingers.
Trump has called on Moscow to hack into Clinton's computers, downplayed criticism of Putin's authoritarian tendencies, tried to suggest that Russia hasn't hacked US systems and promoted foreign policy positions that jibe more closely with Moscow's than Washington's. He's relied on aides with ties to Russia and most recently, quoted an incorrect Russian news report to raise questions about Clinton.
For its part, Russia's ambassador to the United Nations formally complained last month about a top UN official's criticism of Trump and right-wing European politicians.
Trump actively called on Russia to help him against Clinton in July, when he called on Moscow to find missing Clinton emails from her tenure as secretary of state.
"Russia, are you listening?" Trump said from the stage of a rally, calling for a foreign country to interfere in an election, an unprecedented moment in presidential politics.
And yet at Sunday's debate, the Republican candidate floated the possibility that Russia isn't behind the hacking at all, saying that Clinton "doesn't know if it's the Russians doing the hacking. Maybe there is no hacking."
In an interview Wednesday with CNN's Brianna Keilar, Trump campaign manager Kellyanne Conway said the campaign has no knowledge about the hack. But she said Trump is "of course" concerned about the potential of meddling in US politics.
"Are we going to put this back on Donald Trump?" Conway said. "Is he the hacker?"
After Trump threatened at Sunday's debate to jail Clinton if he wins the White House, former chess world champion Garry Kasparov, a fierce Putin critic, took to Twitter to note that Trump seemed to be emulating Putin's style. Kasparov noted that crackdowns on media and political opponents are "also Putin's checklist."
Trump's foreign policy positions
Trump has taken foreign policy positions that analysts say would please Russia, declaring in March that he would consider pulling the US out of NATO because it's "obsolete" and "is costing us a fortune." The 28-member organization, founded in 1949 to defend against the Soviet Union, is the core US-Atlantic security mechanism.
In August, Trump said Russia wouldn't enter Ukraine, despite Moscow's annexation of Crimea in early 2014. He later clarified to say he meant that Russia wouldn't enter Ukraine if he were president.
At Sunday's debate, Trump insisted that Russia is targeting ISIS in Syria, despite repeated assessments by US security officials that Russian troops are spending more time focused on moderate opposition groups, including those backed by the US.
Trump campaign advisers have had ties to Russia. Former campaign chairman Paul Manafort lobbied on behalf of Russian-backed Ukrainian president Viktor Yanukovich. Carter Page, described at one point by the campaign as an informal policy advisor, reportedly had investments in Russian gas company Gazprom and has publicly criticized the US in a speech in Moscow. Trump campaign manager
Conway told CNN's Jake Tapper in September that Page is no longer part of the campaign.
A Trump security adviser, Lt. General Mike Flynn, the retired head of the Defense Intelligence Agency, attended a December gala for the the state-backed Russia Today television network, placed two seats away from Putin, according to Politico.
Trump's refusal to release his tax returns makes it impossible to get a full sense of his investments and whether he has any in Russia, but he does have business ties to Russians.
Trump has also written about trying to build a Trump property in Moscow since 1987 in his book "The Art of the Deal," signing his most recent deal to build in Moscow in 2013, according to the Washington Post.
The Republican candidate worked with Russian oligarchs to stage the Miss Universe pageant to Moscow in 2013. And his son Trump Jr told a real estate investment conference in 2008 that "Russians make up a pretty disproportionate cross-section of a lot of our assets," adding that they "see a lot of money pouring in from Russia."
More recently, the group Democratic Coalition Against Trump posted to YouTube a 2012 interview with Donald Trump Jr. that shows the candidate's son listing various Russian projects the family is interested in, including golf courses and hotels.
"I've been there many times, I've spent quite a bit of time in Moscow looking at deals," Trump Jr. said.