Xiaomi is losing its most high-profile executive, Hugo Barra. The executive will be soon leaving after a three-and-a-half year stint, citing health concerns and a new role.

Xiaomi was briefly the world's most valuable startup and had hopes to be China's equivalent of Apple. But the firm has recently grappled with slowing smartphone sales and fell out of the top five in China for smartphone vendors in 2016, after reaching No. 2 in 2015.

"The last few years of living in such a singular environment have taken a huge toll on my life and started affecting my health," Barra said in the statement on Facebook.

"Seeing how much I've left behind these past few years, it is clear to me that the time has come to return."

Barra said he would officially leave the role after Lunar New Year, which runs until Feb. 2, and take time off before embarking on a new role. He did not specify the role.