A false claim circulating on social media that Democratic presidential candidate Kamala Harris left a 13-year-old girl paralysed after an alleged hit-and-run in San Francisco in 2011 is the work of a covert Russian disinformation operation, according to new research by Microsoft.

Researchers found that the operation created a video, paid an actor to appear as the alleged victim, and spread the claim through a fake website for a non-existent San Francisco news outlet named "KBSF-TV". The Russian group responsible, which Microsoft dubs Storm-1516, is described as a Kremlin-aligned troll farm.

The discovery is a sign of Russia ramping up its foreign influence efforts ahead of the November 5 presidential election, Microsoft said.

A spokesperson for the Russian embassy in Washington did not respond to a request for comment.

"Russian influence operations initially struggled to pivot operations aimed at the Democratic campaign following President Biden’s departure from the U.S. 2024 presidential race," a blog published on Tuesday by Microsoft said.

"In late August, however, elements of prolific Russian actor Storm-1516 began producing content implicating Vice President Harris and Governor Walz in outlandish fake conspiracy theories," Microsoft said, referring to Harris' running mate, Tim Walz.

Storm-1516 is known for producing misleading videos featuring on-screen or voice actors who impersonate whistleblowers or journalists that share false, scandalous information, experts say.

A website for KBSF-TV was created shortly before publishing its first related article about the alleged driving incident, according to online registration records. The claim was circulated on social media platforms, including X.com, using the hashtag #HitAndRunKamala.

The video was also shared on September 3 on X.com by Aussie Cossack, who describes himself as a "Registered foreign agent for Sputnik News," with the message "make this go viral MAGA folks." In total, it is estimated the video has been viewed more than 2.7 million times.

"Many entities within the pro-Russian ecosystem advanced the video and its claims," said Microsoft's Threat Analysis Center. "Storm-1516 relies on some of these personalities, such as Aussie Cossack, to drive amplification of its videos."

Cossack did not immediately respond to a request for comment.

Earlier this month the U.S. Justice Department filed money-laundering charges against two employees of Russian state media network RT for what officials said was a scheme to hire an American company to produce online content to influence the election.

U.S. officials say Russia's goal is to exacerbate U.S. political divisions and weaken public support for American military aid to Ukraine. Harris says if elected she will continue supporting Ukraine in its defence against Russia's invasion.