The computer network used by Democratic presidential candidate Hillary Clinton's campaign was hacked as part of a broad cyber attack on Democratic political organizations, people familiar with the matter told Reuters.

The latest attack, which was disclosed to Reuters on Friday, follows reports of two other hacks on the Democratic National Committee and the party's fundraising committee for candidates for the U.S. House of Representatives.

The U.S. Department of Justice national security division is investigating whether cyber hacking attacks on Democratic political organizations threatened U.S. security, sources familiar with the matter said on Friday.

Campaign officials were involved in crisis talks after the public disclosure of the Justice Department investigation.

Hours after the disclosure, it issued a statement claiming its own cyber security review had found 'no evidence' of a breach.

Spokesman Nick Merrill said: '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.

'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.'

But in an astonishing twist, Yahoo News reported that the campaign had been warned by the FBI it was at risk in March - but refused to turn over details to federal investigators to help them catch the perpetrators.

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In the spotlight: Huma Abedin finds herself in a second email crisis - this time because the campaign of which she is vice-chair has been hacked.

Security risk? Anthony Weiner (pictured with his sister-in-law Heba Abedin), who accompanied his wife Huma Abedin at the Democratic National Convention. Her emails may have been compromised. Trump has mocked him for his sexting scandal

Like! Hillary Clinton gives a thumbs up today after speaking at a campaign rally at Temple University in Philadelphia - but she is likely to be extremely concerned that her campaign's servers were hacked

Serious concern: Her campaign held internal crisis talks as the leak was revealed why she campaigned at Temple University, Philadelphia. It was formerly associated with Bill Cosby, now accused of being a serial rapist

Hillary Clinton and Tim Kaine are campaigning together on a bus tour through Pennsylvania and Ohio starting Friday but her campaign is now facing the prospect of its most intimate secrets being leaked

Hillary and Bill Clinton and Tim Kaine greet rally attendees before speaking to the crowd on Friday

FBI agents met senior Clinton officials in Brooklyn in March to warn them it was the target of cyber attack.

It was weeks before the attack on the Democratic National Committee came to light.

Buy Yahoo News' Michael Isikoff reported Friday that agents asked the campaign to hand over internal computer logs and senior officials' email addresses.

Through lawyers, the campaign refused to give over the information because 'the FBI’s request for sensitive personal and campaign information data was too broad and intrusive', Yahoo News said.

The involvement of the Justice Department's national security division is a sign that the Obama administration has concluded that the hacking was state sponsored, individuals with knowledge of the investigation said.

The Clinton campaign, based in Brooklyn, had no immediate comment and referred Reuters to a comment from earlier this week by campaign senior policy adviser Jake Sullivan criticizing Republican presidential candidate Donald Trump and calling the hacking 'a national security issue.'

The Department of Justice had no comment.

It was not immediately clear what information on the Clinton campaign's computer system hackers would have been able to access.

Hackers, whom U.S. intelligence officials have concluded were Russian, gained access to the entire network of the fundraising Democratic Congressional Campaign Committee, of DCCC, said people familiar with the matter, detailing the extent of the breach to Reuters for the first time.

Access to the full DCCC network would have given the hackers access to everything from emails to strategy memos and opposition research prepared to support Democratic candidates in campaigns for the House.

The hack of the DCCC, which is based in Washington, was reported first by Reuters on Thursday, ahead of Clinton's speech in Philadelphia accepting the Democratic party's nomination. Russian officials could not be immediately reached for comment.

The DCCC said in a statement early on Friday that it has hired cyber security firm CrowdStrike to investigate.

'We have taken and are continuing to take steps to enhance the security of our network,' the DCCC said. 'We are cooperating with federal law enforcement with respect to their ongoing investigation.'

The campaign's staff include Huma Abedin, its vice-chair and Clinton's closest aide.

Her ability to be trusted with secrets has already been questioned by Donald Trump, because of her marriage to Anthony Weiner, the New York mayoral candidate whose career ended in disgrace over sexting.

Drawn into storm: Trump has suggested Huma Abedin cannot be trusted with secrets, but his challenge to the Russian hackers believed to be behind the security breach to produce Hillary Clinton's 30,000 deleted emails led to claims he was inciting foreign espionage

She's out: DNC chair Debbie Wasserman Schultz had to depart in disgrace over her bias against Bernie Sanders, revealed in her leaked emails

The Clintons and Kaine speak to onloookers outside their campaign bus, which features the phrase 'better together'

Wasn't me: Vladimir Putin, who was in Velikiy Novgorod, has denied through the Kremlin that his state was behind the attacks. U.S. security officials say they are almost certain that it was Russian state-sponsored

'Her number one person, Huma Abedin, is married to Anthony Weiner, who's a sleazeball and pervert,' Trump said earlier this week at a press conference in Doral, Miami.,

'I'm not saying that, that's recorded history. I don't like Huma going home at night and telling Anthony Weiner all of these secrets.'

Other staff include Robby Mook, who this week was the first to suggest that Donald Trump was benefiting from the leaks; and John Podesta, the campaign chairman.

It is unknown whether Clinton herself has a campaign email address but any correspondence she had with aides who have one could be vulnerable to release too.

The fact of the hacking will also allow Trump to raise her record of deleting 30,000 emails from her 'homebrew' server after its existence was revealed, a scandal which has severely hit her levels of public trust.

Her number one person, Huma Abedin, is married to Anthony Weiner, who's a sleazeball and pervert. I don't like Huma going home at night and telling Anthony Weiner all of these secrets Donald Trump, earlier this week

The first tranche of emails from the leaks - those from the Democratic National Committee - were released days before the party's Convention in Philadelphia.

They led to the committee chairman, Debbie Wasserman Schultz, quitting in disgrace after her bias against Bernie Sanders was revealed.

Other emails revealed how staff tried to attack Sanders over his religious beliefs, used anti-gay slurs, mocked the name of an African-American assistant and tried to produce a juvenile fake job advert on Craigslist to humiliate Donald Trump.

The disclosure that the Clinton campaign refused to help the FBI comes just a day after the Democratic National Convention put law enforcement center stage on its final night.

But at the time, Clinton herself was under FBI investigation over her handling of the country's secrets when she was Secretary of State.

Clinton was eventually questioned by agents and days later, FBI Director James Comey decided not to recommend that she be prosecuted.

Clinton had used a secret 'homebrew' server stored in the basement of her Chappaqua, New York, home while the was Secretary of State.

Its existence only came to light during the investigation into the death of four Americans - including the US ambassador - during the attack on the diplomatic compound in Benghazi on September 11 2012, when Clinton was Secretary of State.

She handed over roughly 30,000 emails, but deleted the rest, declaring they were 'private' and claiming they included details of 'yoga', and her 'daughter's wedding'.

This week Trump waded into the row over the hacking by inviting the hackers to hand over the missing emails if they had them.

He said he did not know who the hacking was by but said: 'Russia, if you're listening, I hope you're able to find the 30,000 emails that are missing. I think you'll be rewarded mightily by our press!'

Democrats seized on the comments, saying that Trump was inviting foreign espionage, with some even accusing him of treason. The next day Trump said he was being 'sarcastic'.

Meanwhile the Kremlin, whose hardline leader Vladimir Putin has been linked to the hacking, has laughed off claims that Russian state agents carried it out.

NO WONDER CLINTON'S STAFF ARE WORRIED: ANTI-GAY SLURS, MOCKING AN AFRICAN-AMERICAN NAME AND FAKING TRUMP VIDEOS - JUST SOME OF THE HUMILIATING SECRETS REVEALED IN THE FIRST HILLARY LEAKS

Thousands of private emails from the Democratic National Committee were made public when they were published on WikiLeaks.

Among the most damning of the 20,000 emails, staffers make fun of a black woman's name, create a fake Craigslist ad for women interested in working for Donald Trump, and trade favors with superdelegates.

The emails also appear to expose favoritism for presumptive Democratic nominee Hillary Clinton over her chief rival in the primary contest, Senator Bernie Sanders.

In one email, staffers discuss a fake Craigslist advertisement that calls for women who want to work for the Trump Organization.

The email begins: 'Digital created a fake craigslist jobs post for women who want to apply to jobs [at] one of Trump's organizations.'

The job description reads: 'Multiple Positions (NYC area) Seeking staff members for multiple positions in a large, New York-based corporation known for its real estate investments, fake universities, steaks, and wine.

'The boss has very strict standards for female employees, ranging from the women who take lunch orders (must be hot) to the women who oversee multi-million dollar construction projects (must maintain hotness demonstrated at time of hiring).

Administrative assistant at Haddad Brands LaQueenia Gibson (left) is mentioned in one email because of her name, while freelance journalist Fred Lucas (right) is made fun of in another email after requesting an interview

'Title: Honey Bunch (that's what the boss will call you). Job requirements: No gaining weight on the job (we'll take some "before" pictures when you start to use later as evidence).

'Must be open to public humiliation and open-press workouts if you do gain weight on the job. A willingness to evaluate other women's hotness for the boss' satisfaction is a plus.

'Should be proficient in lying about age if the boss thinks you're too old. Working mothers not preferred (the boss finds pumping breast milk disgusting, and worries they're too focused on their children).

'About us: We're proud to maintain a "fun" and "friendly" work environment, where the boss is always available to meet with his employees.

'Like it or not, he may greet you with a kiss on the lips or grope you under the meeting table. Interested applicants should send resume, cover letter, and headshot to jobs@trump.com.

DNC National Finance Director Jordan Kaplan can be seen apparently trading favors with a superdelegate in one email

Luis Miranda, Communications Director for the DNC, responded to the email after being asked for approval on the fake advertisement.

'As long as all the offensive s**t is verbatim I’m fine with it,' he wrote in an email.

In another email thread, DNC staffer Scott Comer and a consulting group employee joke about an administrative assistant at Haddad Brands, named LaQueenia Gibson.

'I'm going to have LaQueenia send out some options for next week,' an executive from Haddad wrote to DNC staffers. 'Hopefully we can all get on the phone and reenergize this event.'

Comer forwarded the email to an employee at Tipah Consulting with the comment: 'Just kill me now.'

The consulting group employee responded: 'LaQueenia is a NAME! I'm sorry, boo. I hope you got a raise with this title.'

Some emails focus on Clinton, issues with her campaign and her own personal emails.

In one email, a staffer called accusations about Hillary being accused of laundering money a 's**t topic' brought on by a 'Bernie Bro'.

'I turned him down flat (and politely) and inquired into opportunities next week to talk about something else,' Pablo Manriquez, the former media booker for the DNC responded to Miranda.

Manriquez, who is no longer on the DNC staff, is told in more than one email to 'f**k off' when responding to messages.

In another leaked email, Clinton's own emails are shared and edited, so they can be approved before they're sent out.

In the message, titled 'For approval: Hillary Clinton emails', DNC staffers say the Hillary Victory Fund and Clinton herself had signed off on the messages, but they needed a final approval.

DNC's research associate Jeremy Brinster openly said in a separate email from April, 'Yes, Super PAC paying young voters to push back online on Sanders supporters', suggesting that the committee was showing favoritism toward Clinton.

The committee, too, appeared to try to expose Bernie Sanders as an Atheist in an attempt to attack his religious views.

'It might may no difference, but for KY and WVA can we get someone to ask his belief,' an email from DNC CFO Brad Marshall reads. 'Does he believe in a God. He had skated on saying he has a Jewish heritage.

'I think I read he is an atheist. This could make several points difference with my peeps. My Southern Baptist peeps would draw a big difference between a Jew and an atheist.'

Kaplan can be seen apparently trading favors with Lucy Moog (pictured) to get an acquaintance's daughter a job in politics

Luis Miranda, Communications Director for the DNC, approved fake Craigslist ads about Donald Trump in one email

Several emails that were leaked discuss the Democratic Party's relationship with various media sites.

In one, DNC staffers are seen conspiring to create false Trump information and release it to Reuters.

'I'm not totally opposed to the idea but it would have to be somewhat controlled. We could set up a 'demo' where we pretend that Trump just said a really offensive thing and then the process of clipping video and getting a release out the door…' DNC Deputy Communications Director Eric Walker says in an email thread.

In another, staffers discuss meeting with MSNBC to discuss how to have the Democratic Party better represented on shows.

Deeper into the leaked emails, the threads get stranger as DNC staffers assess personal issues and interactions with reporters.

After Fred Lucas, a freelance reporter working for Fox News reached out for an interview, several staffers made fun of him among themselves.

One staffer asked his colleagues if there was a 'f**k you' emoji, before another staffer decided the organization was 'not responding at all'.

When Lucas reached out to the DNC again, staffers again laughed at his determination.

'The a*****e from fox emailed us again,' DNC Press Assistant Rachel Palermo wrote to several others. 'I did some research and there's still no "f**k you" emoji, unfortunately.'

In another email, DNC National Finance Director Jordan Kaplan can be seen apparently trading favors with superdelegate Lucy Moog to get an acquaintance's daughter a job in politics.

A superdelegate reached out to Kaplan asking if he or someone from his staff could 'meet with an awesome young person about to graduate from Duke'.

'She is dying to get into the political world. Worked for Ready for Hillary in NYC couple of summers ago. Smart and savvy. Wants to do the DC post college political thing starting in June. Please?' the superdelegate writes.

While vetting DNC donor George Lindemann, Jr (left), staffers bring up his father, George Lindemann (right) who at one time killed horses for insurance fraud

Kaplan responds by trying to make a deal with the superdelegate.

'Ill make you a deal - now that you are a super delegate and all!' he writes. 'Happy to meet with her, but can I get a pass to the EBC for Thursday morning?'

In a later email to the woman he says: 'I will do it and if i cannot have, someone else step in. I'm not that busy. SHHHH.'

Kaplan had several questionable emails in leaked in the WikiLeaks drop, including one where he used a homophobic remark toward another staffer.

'Are we back to the point I can say I love you? Because I'd like to,' DNC staffer Zachary Allen writes to Kaplan.

Kaplan responds: 'I love you too. No homo.'

In another, Kaplan and a DNC staffer discuss a man's sexuality, where Kaplan says the man 'is definitely gay. He swims for the gay and lesbian team in DC.'

'Totes. He gives me daddy vibes,' DNC's Scott Comer responds.

Overall, the DNC staffers appear to be comfortable discussing other people's personal histories and saying offensive remarks to one another.

In an email titled 'Tiny suggestion', staffer Karina Marquez tells Comer: 'Eat my butt'.

In another, staffers discuss buying a gift basket for a former staffer and decide that the smaller it is, the better.

'He didn't work with us that long,' Kaplan says, suggesting a gift basket below $50.

Comer responds: 'Maybe even less than that since he's so skinny.'

In one email, a group of staffers discuss vetting DNC donor George Lindemann, Jr, when his father, George LIndemann is mentioned because he killed horses for insurance fraud.