As part of changes after a $44bn takeover of the social media site, Musk said it was "essential to defeat spam/scam".

A blue tick mark next to a username - normally for high-profile figures - is currently free.

The move could make it harder to identify reliable sources, say critics.

Musk, the world's richest person, added that paid users would have priority in replies and searches and half as many advertisements.

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"Power to the people! Blue for $8/month," the billionaire tweeted, dismissing the old blue tick verification method as a "lords and peasants system."

Twitter's former method of verifying users for a blue tick included a short online application form and was reserved for those whose identities were targets for impersonation, such as celebrities, politicians and journalists.

The company introduced the system in 2009, after it faced a lawsuit accusing it of not doing enough to prevent imposter accounts.

But Musk is facing a hefty challenge as he works to overhaul Twitter's business, which has not posted a profit in years.

He has said he wants to reduce Twitter's reliance on advertising, even as some companies have grown concerned about advertising on the site under his leadership.

"We need to pay the bills somehow!"

General Motors - a rival of Musk's electric car company Tesla - said last week it was suspending advertising on the site.

Meanwhile, some other major brands have more quietly put a temporary halt to advertising on the platform as they wait to see how Musk's changes play out. 

On Monday, one of the world's biggest advertising companies, IPG, advised its clients to suspend Twitter adverts for a week, citing a need for more clarity on Twitter's plans to ensure "trust and safety" on the platform. IPG is given billions per year by some of the world's biggest brands to handle their marketing budgets.

The charge for blue tick privileges drew scepticism after original reports that said the charge could be $20 monthly.

Many on the platform echoed the statement of author Stephen King, who wrote in response to reports of changes that Twitter "should pay me instead".

Musk responded to King, saying, "We need to pay the bills somehow!"

BBC