TEL AVIV — An Israeli watchdog group has found a network of hundreds of social media accounts, many of them fake, used to smear opponents of Prime Minister Benjamin Netanyahu in next week’s election and to amplify the messages of his Likud party, according to a report to be released Monday.

The messages posted on the network’s Twitter and Facebook accounts are frequently reposted by prominent Likud campaign officials and by the prime minister’s son, Yair Netanyahu, the report says.

The watchdog group, the Big Bots Project, an independent organization that aims to expose the malicious use of social media, found no direct links between the network and Mr. Netanyahu, his party or his son, but said it appeared to operate in coordination with the party and Mr. Netanyahu’s re-election campaign.

“The network operates through manipulations, slander, lies and spreading rumors,” the report said. “On its busiest days, the network sends out thousands of tweets a day.”