A network of hundreds of social media accounts has been working to boost Prime Minister Benjamin Netanyahu's re-election campaign and smear his opponents ahead of next week's election, the New York Times and Israeli daily Yedioth Ahronoth reported on Monday, citing a report by a watchdog group.

The report by the Big Bots Project was written with assistance by the Israeli Alliance, a liberal-leaning organization, the New York Times said. While it found no direct links between the network and Netanyahu or his Likud party, it said the accounts appeared to work in tandem with one another and in coordination with Likud's election campaign.

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The network included 154 accounts using fake names, with another 400 accounts suspected of being fake, with all of them apparently being operated by real people and with the posts receiving over 2.5 million hits, the report said. The network has posted about 130,000 tweets since the election was announced, the report said.

The network's activity has increased nearly fivefold since the election was called in December, and it is particularly active at "climactic moments for Netanyahu," the newspaper quoted the report as saying. Its messages were reposted by high-profile people linked to the Likud campaign, including Yair Netanyahu, the prime minister's son, who is an unofficial adviser to the campaign and retweeted members of the network 154 times, according to the report.

All the accounts are linked to one person, Yitzhak Haddad of Ashdod, according to the report, which cited a YouTube channel to which he is in active subscriber that features a message offering money for "responding on Facebook and on the internet with political messages. You just get political messages and you post them."

Haddad admitted to a private investigator that he created videos and posted them online. Asked whether the activity was paid for, he replied, "Yes. [I] post them to Twitter, post it all kinds of places." He also gave an idea of the scale of the operation: "I don't want to say tens of millions," he said, "but loads of money is being invested here. It takes money, there's no volunteering here." He added that he was connected to "very senior people" in Likud. Haddad's attorney said he denied "what was attributed to him" and threatened a million-dollar libel lawsuit against anyone publishing otherwise.

The network has devoted much of its activity to smearing Netanyahu's primary rival in the election, Benny Gantz, the report said. The evening before the attorney general announced that Netanyahu would be indicted, the network amplified a Facebook post by a woman saying Gantz sexually harassed her when they were in high school, a claim Gantz denied and for which no additional evidence has emerged. Last week, many of the accounts began, almost at the same time, posting messages alleging that Gantz was mentally ill – a claim made in a Likud video clip.

Netanyahu responded to the report later on Monday and denied that Likud had been using fake social media accounts. "Not one is fake, they're all real people," Netanyahu said. Netanyahu went on to accuse the media of spreading a "blood libel" and supporting his rivals, claiming that "all the channels, almost all of the time" are spreading fake news. Earlier, a Likud spokesman denied the party ran a network of fake accounts and said it had no connection to Haddad.

Kahol Lavan, the political alliance led by Gantz, was quick to respond to Netanyahu's remarks and accused the prime minister of trying to steal the election. "We have never seen a prime minister who lies and slanders so much. He should explain, where do the millions of shekels that fund his network of lies come from? And how has he paid them without reporting it?" Kahol Lavan said in a statement.