Systrom's and Krieger's departures from Facebook's fastest-growing revenue generator come just months after the exit of Jan Koum, co-founder of Facebook-owned messaging service WhatsApp, leaving the social network without the developers behind two of its biggest services.

They also come at a time when Facebook's core platform is under fire for how it safeguards customer data and as younger users increasingly prefer alternative ways to stay in touch with family and friends.

Kevin Systrom wrote in a blog post that he and Mike Krieger planned to take time off and explore their curiosity and creativity again. Their announcement came after frequent clashes with Facebook CEO Mark Zuckerberg over the direction of Instagram.

"I've learned a lot working with them for the past six years and have really enjoyed it," Zuckerberg said. "I wish them all the best and I'm looking forward to seeing what they build next."

From leaders to plain users

"Building new things requires that we step back, understand what inspires us and match that with what the world needs," Systrom said in a statement. "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."

Facebook bought Instagram in 2012, just before going public. It secured the photo-sharing app for $1 billion (€850 million).

At the time, Instagram was ad-free, with a loyal following of 31 million users who were all on mobile devices.

hg/aos (AFP, Reuters)