A small fraction of the vast Twitter user base is spreading majority of the fake news, with conservatives and older people sharing misinformation more, according to a study of over 16,000 US Twitter accounts.

The study, published in the journal Science, found that 16 of the 16,442 accounts examined tweeted out nearly 80 percent of the misinformation masquerading as news.

About 99 percent of the Twitter users spread virtually no fake information in the most heated part of the election year in 2016, said David Lazer, a professor at the Northeastern University in the US.

Spreading fake information "is taking place in a very seamy, but small, corner of Twitter," Lazer said.

He said misinformation "super sharers" flooded Twitter: an average of 308 pieces of fakery each between August 1 and December 6 in 2016.

It is not just few people spreading it, but few people reading it, Lazer said.

"The vast majority of people are exposed to very little fake news despite the fact that there is a concerted effort to push it into the system," he said.

The researchers found the 16,442 accounts they analysed by starting with a random pool of voter records, matching names to Twitter users and then screening out accounts that appeared to not be controlled by real people.

Their conclusions are similar to a study earlier this month that looked at the spread of false information on Facebook.

It also found that few people shared fakery, but those who did were more likely to be over 65 and conservatives.

That makes this study more believable because two groups of researchers using different social media platforms, measuring political affiliation differently and with different panels of users came to the same conclusion, said Yonchai Benkler, co-director of Harvard Law School's centre on the internet and society.

Unlike the earlier Facebook study, Lazer did not interview the people but ranked people's politics based on what they read and shared on Twitter.

The researchers used several different sources of domains for false information masquerading as news -- not individual stories but overall sites -- from lists compiled by other academics and BuzzFeed.

The team found that among people they categorised as left-leaning and centrists, fewer than five percent shared any fake information.

Among those they determined were right-leaning, 11 percent of accounts shared misinformation masquerading as news. For those on the extreme right, it was 21 percent.