US Democratic presidential candidate Hillary Clinton says Russian intelligence services hacked into Democratic National Committee computers and she has accused Republican contender Donald Trump of showing support for Russian President Vladimir Putin.
"We know that Russian intelligence services hacked into the DNC and we know that they arranged for a lot of those emails to be released, and we know that Donald Trump has shown a very troubling willingness to back-up Putin, to support Putin," Mrs Clinton said in an interview with Fox News on Sunday.
The United States has not publicly accused Russia of being behind the hack of Democratic Party computers.
Cyber security experts and US officials, however, said they believed Russia engineered the release of the emails to influence the November 8 US presidential election.
Asked if she believed Mr Putin wanted Mr Trump to win the White House, Mrs Clinton said she was not going to jump to that conclusion.
"But I think laying out the facts raises serious issues about Russian interference in our elections, in our democracy," Mrs Clinton said.
The US would not tolerate that from any other country, especially one considered an adversary, she said.
"For Trump to both encourage that and to praise Putin despite what appears to be a deliberate effort to try to affect the election I think raises national security issues," she said.
The New York businessman has praised Mr Putin, saying he was a stronger leader than US President Barack Obama, a Democrat.