A computer system used by Democratic presidential nominee Hillary Clinton's campaign was "accessed" as part of a larger cyberattack on Democratic Party organisations, people familiar with the matter told Reuters on Friday (29 July). The latest attack follows a series of high-profile data breaches involving the Democratic National Committee (DNC) and the Democratic Congressional Campaign Committee (DCCC), the fund-raising arm for the House Democrats.

News of the attack also came just hours after the DCCC confirmed reports that it was hacked as well, saying the breach was similar to the one that targeted the DNC.

The Clinton campaign, however, said in a statement that there was no evidence so far that its internal systems were compromised.

"An analytics data program maintained by the DNC, and used by our campaign and a number of other entities, was accessed as part of the DNC hack," Clinton press secretary Nick Merrill said in a statement. "Our campaign computer system has been under review by outside cyber security experts. To date, they have found no evidence that our internal systems have been compromised."

Meanwhile, the New York Times reports that the breach "appears to have come from Russia's intelligence services," citing an anonymous federal officer.

However, Kremlin has sharply denied any involvement in the attacks with a top official stating that the accusations are "a vivid example of the use of Russophobia for the election purposes in the US."

The FBI is currently investigating the attacks but has declined to specify the target.

"The FBI is aware of media reporting on cyber intrusions involving multiple political entities, and is working to determine the accuracy, nature and scope of these matters," the FBI said in a statement. "The cyber threat environment continues to evolve as cyber actors target all sectors and their data. The FBI takes seriously any allegations of intrusions, and we will continue to hold accountable those who pose a threat in cyberspace."

Reuters also reported that the US Department of Justice national security was also investigating whether the cyberattacks targeting the Democratic Party organizations had threatened national security.

Just days before the Democratic convention began, thousands of hacked internal emails from the DNC were published by WikiLeaks on 22 July, revealing that some Democratic Party officials favoured Hillary Clinton over her primary opponent, Bernie Sanders. The leak also led to the resignation of DNC chair, Debbie Wasserman Schultz.

According to CrowdStrike, a cybersecurity firm initially hired by the DNC to investigate the breach, as well as other security firms, evidence suggests that the Russian government was involved in the DNC hack reportedly carried out by hacker groups "Cozy Bear" and "Fancy Bear."

Republican presidential nominee Donald Trump also sparked intense backlash after calling on Russia to find Clinton's missing emails.

"Russia, if you're listening, I hope you're able to find the 30,000 emails that are missing," Trump said at a news conference in Florida. "I think you will probably be rewarded mightily by our press."

The GOP nominee was slammed by the Clinton campaign who accused him of calling on a foreign rival to "commit espionage in the US." Trump later claimed that he was "being sarcastic."