The founders of social media platform Instagram have resigned without offering any explanation.

Chief Executive Kevin Systrom and Chief Technical Officer Mike Krieger announced late on Monday that they were leaving the smartphone photo-sharing service bought by Facebook six years ago for a billion dollars.

Facebook shares were down 2 per cent from Monday's close at the opening bell on Tuesday.

The pair's sudden departure follows frequent clashes with Facebook CEO Mark Zuckerberg over product changes to Instagram, including changes to comments and how posts are shared between the two networks, according to ReCode.

'We're planning on taking some time off to explore our curiosity and creativity again. 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,' Systrom said in a statement late Monday night.

Systrom, 34, is worth $1.4 billion, while the 32-year-old Krieger's wealth is estimated at about $500 million, according to Forbes.

Instagram co-founders Kevin Systrom (left) and Mike Krieger (right) resigned Monday night

Reports have been swirling of 'clashes' between the men and Facebook CEO Mark Zuckerberg

'Mike and I are grateful for the last eight years at Instagram and six years with the Facebook team,' Systrom said.

'We've grown from 13 people to over a thousand with offices around the world, all while building products used and loved by a community of over one billion. We're now ready for our next chapter.'

'We remain excited for the future of Instagram and Facebook in the coming years as we transition from leaders to two users in a billion,' Systrom wrote in a statement.

'We look forward to watching what these innovative and extraordinary companies do next.'

The two men became overnight multi-millionaires when Facebook acquired Instagram in 2012, with Krieger going on to wed Kaitlyn Trigger in 2015 and Systrom marrying Nicole Schuetz in 2016.

Their departure from Instagram has not been a surprise for some tech commentators, who report that there has been tension between the pair and Facebook's leadership.

Business Insider's Tech Editor Alexei Oreskovic said the timing of their departure - both of them leaving at the same time - and the fact that neither Mark Zuckerberg or Facebook COO Sheryl Sandberg are mentioned in their statement are clear signs of 'bad blood'.

According to Tech Crunch, it was Facebook's broken promise to allow Instagram to remain autonomous that was the main cause for their departure.

'Facebook had agreed to let it run independently as part of the acquisition deal. But in May, Instagram’s beloved VP of Product Kevin Weil moved to Facebook’s new blockchain team and was replaced by former VP of Facebook News Feed Adam Mosseri — a member of Zuckerberg’s inner circle,' the website wrote.

Krieger wed Kaitlyn Trigger (left) in 2015 and Systrom married Nicole Schuetz (right) in 2016

The CEO and CTO are departing with no explanation after selling to Facebook six years ago but said they are 'ready for our next chapter'. Systrom is seen above

Facebook executives who have left in the past year Facebook is notorious for retaining its top talent, but the past year has seen a steady dribble of executive departures as the company comes under increasing public scrutiny and investor pressure. The high-profile departures include: WhatsApp cofounder Brian Acton, who left in September 2017. Acton said he intended to start a foundation "focused at the intersection of nonprofit, technology and communications." WhatsApp cofounder Jan Koum, who left in April 2018. Koum reportedly clashed with parent company Facebook over data privacy and the messaging app’s business model. VP of Communications and Public Policy Elliot Schrage, who left in June 2018. Schrage gave no concrete reason for stepping down, but had come under criticism for Facebook's slow response to the Cambridge Analytica scandal. Chief Security Officer Alex Stamos, who left in August 2018. Stamos left to join Stanford University full-time as a teacher and researcher. He was an an outspoken security and privacy advocate and had reportedly clashed with other Facebook executives about how much to reveal to the public about Russian election interference efforts on the platform. Instagram cofounders Kevin Systrom and Mike Krieger, who left in September 2018. The pair said they were leaving to 'explore our curiosity and creativity again' and had reportedly butted heads with Zuckerberg over Instagram's autonomy and changes to the service's features. Advertisement

Dave Lee, BBC North America technology reporter, wrote: 'If being mocked for brazenly stealing ideas from Snapchat wasn't grating enough for Mr Systrom and Mr Krieger, the pressure to make Instagram more like Facebook has apparently pushed them to breaking point.'

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

CEO Mark Zuckerberg called Systrom and Krieger 'extraordinary product leaders' and said he was looking forward 'to seeing what they build next.'

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

The platform has been a hit with young internet users, an audience that Facebook is keen to keep in its fold.

Facebook has dealt with multiple challenges over recent years, including concerns over user privacy and the spread of 'fake news'.

Zuckerberg called the pair 'extraordinary product leaders' and said he was looking forward 'to seeing what they build next'. Pictured: Krieger (left) with Systrom

In March, Facebook faced a public relations disaster after it came to light that Cambridge Analytica may have harvested the data of up to 87 million users.

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.

In July, the company reported declining growth in revenue and users, disappointing investors and sending Facebook's stock plummeting.

Earlier this year, WhatsApp co-founder Jan Koum also left Facebook, which bought the smartphone messaging service for $19 billion in February 2014.

Koum said in a post on his Facebook page that he was taking time off to pursue interests such as collecting air-cooled Porsches, working on cars and playing ultimate Frisbee.

Reports indicated that a disagreement with Facebook over the privacy of user data may have also been a factor in Koum's decision to quit his position as a high-ranking executive and likely leave his seat on the board at the leading online social network.