Instagram co-founders Kevin Systrom and Mike Krieger have announced that they are leaving the photo-sharing app bought by Facebook six years ago, setting a new test for the parent company as it works to quell mounting turmoil.

“Mike and I are grateful for the last eight years at Instagram and six years with the Facebook team,” Systrom said in a statement late Monday, following a report on the departure in The New York Times.

“We're planning on taking some time off to explore our curiosity and creativity again.”

Systrom, 34, created the app in 2010 with 32-year-old Krieger, now the outgoing “chief technical officer”, when they were students at Stanford University in the heart of Silicon Valley.

Facebook CEO Mark Zuckerberg praised the departing Instagram leaders for “their combined creative talents”, saying “I've learned a lot working with them.”

“I wish them all the best and I'm looking forward to seeing what they build next,” Zuckerberg said in a statement released by Facebook.

Systrom's fortune is valued at $1.4 billion by Forbes.

“Building new things requires that we step back, understand what inspires us and match that with what the world needs; that's what we plan to do,” the statement said — though several US media outlets attributed the split to a disagreement with executives at Facebook.

“We're now ready for our next chapter,” the statement continued.

Instagram in June announced it passed a billion active users, and unveiled a new long-form video feature in a bid to attract “creators” like those on YouTube.

It became the fourth Facebook platform to eclipse the billion-user mark, including the namesake social network with more than two billion users, and the messaging applications WhatsApp and Messenger.

Facebook acquired Instagram in April 2012 for a combination of cash and stock worth some $1 billion at the time.

Questions of autonomy

Instagram has been a hit with young internet users, an audience that Facebook is keen to keep in its fold. The Instagram co-founders have reportedly clashed with Facebook's leadership over the photo-sharing service's autonomy within the company, according to The Wall Street Journal citing people close to the matter.

The departures come as Facebook grapples with the worst crisis in its history, vilified for not more zealously guarding the information which users share.

Many see Facebook as having been a top vehicle for spreading false information in recent years, and of being used by nefarious interests intent on swaying elections such as the poll which put President Donald Trump in the White House.

The Cambridge Analytica public relations disaster — in which Facebook admitted that up to 87 million users may have had their data hijacked by the British consultancy — came on top of widespread criticism of the social network's propensity to spread and accentuate large amounts of completely false information.

Facebook is facing multiple inquiries from US and British regulators about the Cambridge Analytica user data scandal, and Zuckerberg was grilled by the European Parliament and the US Congress earlier this year.