A top security officer for Twitter resigned on Thursday as new owner Elon Musk’s revamp of the platform saw a boomlet of fake accounts, drawing a rare warning from US regulators.

"I’ve made the hard decision to leave Twitter," tweeted chief security officer Lea Kissner, who reportedly stepped down with other key privacy or security executives.

The walk-outs came a day after the chaotic launch of new features introduced by Musk following his $44 million buyout of the influential one-to-many messaging app.

{ Read: Can Elon Musk Spur Cybersecurity Innovation at Twitter? }

It unveiled its long-awaited Twitter Blue subscription service, which allows users to pay $7.99 per month for a coveted blue tick, as well as a separate gray "official" badge for some high-profile accounts.

But Musk drew criticism when he scrapped the new gray label almost immediately, overshadowing the launch of the pay service, which is currently only available on the mobile app on iPhones and in the United States.

The launch also saw the rise of a flurry of fake accounts as users used the opportunity to impersonate celebrities and politicians such as NBA star Lebron James or former British prime minister Tony Blair.

The chaos drew a rare warning from the Federal Trade Commission, the US authority that oversees consumer safety which has put Twitter under watch for past security and privacy breaches.

"We are tracking recent developments at Twitter with deep concern," a spokesperson for the FTC said in a statement.

"No CEO or company is above the law, and companies must follow our consent decrees," the spokesperson added, referring to past commitments by Twitter to obey US privacy rules.

The boss of Tesla and SpaceX fired half of the 7,500 employees of the California company a week ago, ten days after buying the site and becoming its sole owner.

For the first time since the layoffs, Musk on Thursday addressed his remaining employees and urged them to help the site reach one billion users, according to employee text messages seen by AFP.

He also announced that he was ending work- from-home policies at Twitter, which had been a widespread practice at the San Francisco-based company.

“If you don’t show up at the office, resignation accepted,” he reportedly told employees.