Sanders supporters seethe over Clinton's leaked remarks to Wall St.

Clinton, who needs Sanders' coalition of young and left-leaning voters to propel her to the presidency, pushes for open trade and open borders in one of the speeches, and takes a conciliatory approach to Wall Street, both positions she later backed away from in an effort to capture the popular appeal of Sanders' attacks on trade deals and powerful banks.

The excerpts of remarks by the former secretary of state, made in 2013 and 2014 in closed-door meetings where audiences paid to attend, were published online on Friday by WikiLeaks, which sourced them to the email account of John Podesta, Clinton's campaign chairman.

Reuters could not independently verify the authenticity of the speech transcripts. Clinton has previously declined to release any such transcripts.

"This is a very clear illustration of why there is a fundamental lack of trust from progressives for Hillary Clinton,” said Tobita Chow, chair of the People's Lobby in Chicago, which endorsed Sanders in the primary election.

"The progressive movement needs to make a call to Secretary Clinton to clarify where she stands really on these issues and that’s got to involve very clear renunciations of the positions that are revealed in these transcripts,” Chow said.

The revelations were quickly overshadowed by the release of an 11-year-old recording of Donald Trump, the Republican presidential nominee, making lewd comments about women.

Clinton has worked hard to build trust with so-called progressives, adopting several of Sanders' positions after she bested him in the primary race. The U.S. senator from Vermont now supports his former rival in the Nov. 8 general election against Trump.

Still, Clinton has struggled to win support from young "millennials" who were crucial to Sanders' success, and some Democrats expressed concern that the leaks would discourage those supporters from showing up to vote.

“That is a big concern and this certainly doesn’t help,” said Larry Cohen, chair of the board of Our Revolution, a progressive organisation formed in the wake of Sanders’ bid for the presidency, which aims to keep pushing the former candidate's ideas at a grassroots level. "It matters in terms of turnout, energy, volunteering, all those things."

The Clinton campaign said it would not confirm the accuracy of the documents released by WikiLeaks and its founder, Julian Assange.

"We are not going to confirm the authenticity of stolen documents released by Julian Assange, who has made no secret of his desire to damage Hillary Clinton," said Glen Caplin, a campaign spokesman.

"Guccifer 2.0 has already proven the warnings of top national security officials that documents can be faked as part of a sophisticated Russian misinformation campaign," he said, referring to the hacker or hacking group that altered some data stolen from the Democratic National Committee before making it public earlier this year.

The U.S. government on Friday formally accused Russia of a campaign of cyber attacks against Democratic Party organizations ahead of the election.

The origin of the leaks did not dampen social media criticism of the speeches by some.

"Bernie was right about Hillary,” wrote Facebook user Grace Tilly, “she’s a tool for Wall Street.”

“Clinton is the politicians’ politician - exactly the Wall Street insider Bernie described,” wrote Facebook user Brian Leach.

Spokesmen for Sanders did not respond to requests for comment. NBC News quoted a statement from Sanders saying he would work to advance the Democrats' policy platform.

"Whatever Secretary Clinton may or may not have said behind closed doors on Wall Street, I am determined to implement the agenda of the Democratic Party platform which was agreed to by her campaign," the statement said.

Democratic strategist Steve Elmendorf said progressive voters would still choose the former first lady, even with misgivings.