World Bulletin / News Desk

White House hopeful Hillary Clinton expressed "grave" concern Monday about reports that Russia has been interfering in the US electoral process through invasive cyber attacks on the Democratic Party.

The possibility of Russian involvement in cyber intrusions that were revealed in July "raises some grave questions about potential Russian interference with our electoral process," Clinton told reporters on her campaign plane as she flew to a rally in Illinois.

Clinton stopped short of using the term cyber-war, but sternly described the Russian interference as "a threat from an adversarial foreign power."

The Democratic nominee, locked in a battle for the presidency with Donald Trump, also blasted her Republican rival for encouraging Moscow to spy on her.

"We've never had a foreign adversarial power be already involved in our electoral process, (and) we've never had a nominee of one of our major parties urging the Russians to hack more."

Clinton, pointed to the "consensus" by US intelligence officials and experts that the hack was orchestrated by Russian intelligence.

The Washington Post reported that US authorities were probing a covert Russian operation that included a cyber attack on voter registration systems in Arizona.

In a comprehensive, 20-minute series of questions and answers that could be interpreted as her first press conference in 275 days, she also addressed the FBI's recent release of notes about its interview with the candidate over her emails on a private account, and her thoughts about the Clinton Foundation.