More than 80 fact-checking organisations Wednesday urged online video platform YouTube to better combat disinformation, offering to help debunk false statements.

"Every day, we see that YouTube is one of the major conduits of online disinformation and misinformation worldwide," said the groups spanning the globe, from Politifact and the Washington Post in the United States to the Kenya-based Africa Check.

Videos containing false information had gone "under the radar of YouTube's policies, especially in non-English speaking countries", they said in an open letter to YouTube chief Susan Wojcicki.

"We urge you to take effective action against disinformation and misinformation... and to do so with the world's independent, non-partisan fact-checking organisations," they added.

"Our experience as fact-checkers together with academic evidence tells us that surfacing fact-checked information is more effective than deleting content."

It also urged the platform to make sure its recommendation algorithm did not actively promote disinformation to its users.

YouTube spokesperson Elena Hernandez defended the platform, saying that fact checking was a "crucial tool", but just "one piece of a much larger puzzle to address the spread of misinformation".

"Over the years, we've invested heavily in policies and products in all countries... to connect people to authoritative content, reduce the spread of borderline misinformation, and remove violative videos," she added.

She said YouTube had seen "important progress".

Japan firefighter punished for YouTube side hustle

A Japanese firefighter moonlighting as a gaming YouTuber had cold water poured on his career by public officials, who uncovered the secret side hustle by identifying his voice in the lucrative videos.

An anonymous tip-off prompted Wakayama city in western Japan to launch an investigation into the 33-year-old's channel, which had around 15,000 subscribers.

But because the firefighter never appeared on screen, a local official had to painstakingly comb through the clips for vocal clues to his identity, the city said.

The man's salary was cut in punishment for contravening a law limiting public workers' engagement in commercial activities.

Over a 10-month period he had uploaded more than 300 videos, typically showing him playing multi-player strategy games -- racking up around 1.15 million yen ($9,970) in advertising revenue.

"We don't necessarily think it's a bad thing that he was a YouTuber," city official Hidetaka Amano told AFP on Wednesday.

"But it's the fact he was profiting from ads, some of which could be inappropriate in nature."

His actions, Amano said, had "betrayed the trust of residents in Wakayama".