LONDON, June 3 (Reuters) - Russia has stepped up an online disinformation campaign which takes aim at France and the upcoming Paris Olympics, Microsoft ( MSFT ) said in a blog post published on Sunday.

The campaign, which includes falsified news websites and a feature-length documentary film, is specifically designed to denigrate the reputation of the International Olympic Committee (IOC) and create the impression that the summer games will be marred by violence, Microsoft ( MSFT ) said.

"The most worrisome disinformation advanced by pro-Russian actors has sought to impersonate militant organisations and fabricate threats to the Games amidst the Israel-Hamas conflict," the company said.

Russia's embassy in London did not respond to an emailed request from Reuters for comment.

Microsoft ( MSFT ) said it had found instances in late 2023 of known Russian disinformation actors posting "likely digitally generated" images purporting to show graffiti in Paris which threatened violence against Israelis attending the Olympics, some of which referenced the 1972 killings by Palestinian militants of 11 Israeli Olympians in Munich.

The campaigns were carried out by two Russian-backed entities Microsoft ( MSFT ) said it tracks as Storm-1679 and Storm-1099, which is also known as "Doppleganger". Using an array of 15, falsified, French news websites, Doppleganger amplified Russian claims of IOC corruption and potential violence at the games, Microsoft ( MSFT ) said.

In June last year, the group Microsoft ( MSFT ) tracks as Storm-1679 produced a feature-length film called "Olympics Has Fallen" which the company said was designed to disparage IOC leadership.

The film, Microsoft ( MSFT ) said, was narrated with fake AI-generated audio of American actor Tom Cruise, and used the personalised video message website Cameo to trick other U.S. celebrities into endorsing the film.

The effort "clearly signalled the content's creators committed considerable time to the project and demonstrated more skill than most influence campaigns we observe," Microsoft ( MSFT ) said.

"The Kremlin's propaganda and disinformation machine is unlikely to hold back in leveraging its network of actors to undermine the Games as the Olympics draw near," the company added.

The campaign increased late last year, following the decision by the IOC to allow Russian athletes to compete in the games as neutral competitors, Microsoft ( MSFT ) said.