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A computer data program used by Hillary Clinton’s campaign was hacked, the campaign said Friday in the latest revelation in a series of cyber-attacks on Democratic Party properties.

Reuters first reported the cyber attack, and said a computer network used by the Clinton campaign was hacked. Federal officials confirmed to NBC News that the Clinton campaign was hacked. The Clinton campaign said a program used by its campaign was breached, but it said no evidence has been found that the campaign's internal systems were broken into.

"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 campaign spokesman 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," Merrill said.

The FBI said Friday it is investigating. "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.

Related: Hack of Democratic Congressional Campaign Committee 'Similar' to DNC Breach

A Clinton aide said the hackers had access to had access to the analytics program's server for approximately 5 days. The program is used to conduct voter analysis. It couldn't have been used to access internal campaign email or other communications or computers, the aide said, citing an outside security expert.

A spokesman for the Donald Trump campaign said Friday: "This seems to be a problem wherever Hillary Clinton goes. Hopefully this time there wasn't classified or top secret information that puts American lives at risk."

News of the hack comes after cyber attacks on Democratic Party groups, including the Democratic National Committee and the Democratic Congressional Campaign Committee's computer system.

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The DCCC confirmed the hack Friday and said it was "similar" to the cyber attack on the DNC. The hack on the DNC has been blamed on the Russian government.

A senior U.S. official told NBC News that the FBI is investigating the intrusion on the Democratic Congressional Campaign Committee's computer system but that agents have not yet found a link to the earlier DNC hack.

The Kremlin has denied it is behind either breach — and a top official responded to the allegations on Friday by denouncing a "poisonous anti-Russian" narrative coming out of Washington.

The disclosure that the DCCC was hacked escalated concern among U.S. national security officials that the intrusions are aimed at swaying the outcome of the presidential election.

Related: Could Russian Hackers Spoil Election Day?

The DCCC, which raises money for Democrats running for House seats, said in a statement that it has retained the forensic investigation firm CrowdStrike, which was also retained by the DNC. The firm concluded two Russian security agencies had hacked into its servers and internal files.

"Based on the information we have to date, we've been advised by investigators that this is similar to other recent incidents, including the DNC breach," DCCC spokeswoman Meredith Kelly said in a statement.

"The DCCC takes this matter very seriously. With the assistance of leading experts we have taken and are continuing to take steps to enhance the security of our network in the face of these recent events. We are cooperating with the federal law enforcement with respect to their ongoing investigation."

Days before the Democratic convention that kicked off Monday, the website WikiLeaks published nearly 20,000 internal emails from Democratic National Committee officials.

Some of the emails appeared to show that some officials favored the Clinton campaign over her primary opponent, Bernie Sanders. The emails inflamed suspicions among some Sanders supporters, and DNC chair Debbie Wasserman Schultz announced she would resign.

WikiLeaks did not say where it got the emails it released.

As NBC News reported this week, senior U.S. national security officials are confident that Russian intelligence agencies hacked the DNC but have not determined if those agencies gave the material to WikiLeaks for the pre-convention email release.

Related: Why Experts are Sure Russia Hacked the DNC Emails

Trump further fanned the flames of speculation when he seemed to invite Russia to release any Clinton emails they might have. The comments were condemned as extremely irresponsible in inviting the Russian government to commit espionage against the U.S.

Trump later called his remarks a "joke."

Russian President Vladimir Putin has complimented Trump in recent weeks. Trump has in the past praised Putin.

Trump last week in an interview with The New York Times suggested that the U.S. would not necessarily defend new NATO members in the Baltics in the event of Russian attack if he were elected to the White House.

Trump said in the interview that doing so would depend on whether those countries had "fulfilled their obligations to us" in terms of their financial contributions to the alliance.

NATO was formed during the Cold War to protect nations from the then-Soviet Union. NATO's treaty states that an attack on one member state constitutes an attack on all, a principle enshrined in Article 5 of the alliance's treaty.