The head of the Democratic National Committee said on Tuesday the organization had been hacked by Russian state-sponsored agents who were trying to influence the U.S. presidential election, after a similar leak in July roiled the party.
A link to the documents was posted on WikiLeaks' Twitter account and attributed to alleged hacker Guccifer 2.0.
The release came during a presentation on Tuesday from a person speaking on behalf of Guccifer 2.0 at a London conference on cybersecurity, Politico reported.
Reuters could not immediately access the documents.
"There's one person who stands to benefit from these criminal acts, and that's Donald Trump," the Republican presidential nominee, DNC interim Chairwoman Donna Brazile said in a statement. "Not only has Trump embraced (Russian President Vladimir) Putin, he publicly encouraged further Russian espionage to help his campaign."
Trump in July invited Russia to dig up emails from Clinton's time as secretary of state, prompting Democrats to accuse him of urging foreigners to spy on Americans. He later said he had been speaking sarcastically.
Debbie Wasserman Schultz resigned as DNC chair on the eve of July's Democratic National Convention after WikiLeaks published a trove of hacked DNC emails that showed party officials favoring eventual nominee Hillary Clinton over Sen. Bernie Sanders during the party's nominating contests. Three other senior officials also stepped down from the DNC after the leak.
"We have been anticipating that an additional batch of documents stolen by Russian agents would be released," said Brazile, who took over from Wasserman Schultz on an interim basis.
Democratic Party sources said the party and Clinton's presidential campaign were deeply concerned about possible publication by WikiLeaks or other hackers of a new torrent of potentially embarrassing party information ahead of the Nov. 8 election.