Four senior Twitter executives are leaving the media company, CEO Jack Dorsey has tweeted.
It's the biggest leadership changes since Dorsey returned as chief executive as he struggles to revive the company's growth.
Media head Katie Jacobs Stanton, product head Kevin Weil, the head of the engineering division, Alex Roetter, and HR head Brian "Skip" Schipper will all leave the company, he said.
Addressing what he called inaccurate press rumours, Dorsey praised the four executives and said he was sad to announce their departures.
Twitter's stock has fallen nearly 50 percent since Dorsey's return last year and is now trading below its IPO price amid concern the company has failed to significantly boost its user base despite a quicker pace of product rollouts under Dorsey.
On Sunday night (local time) Jason Toff, who heads Twitter's video streaming service, Vine, tweeted that he was also leaving Twitter to join Google to work on virtual reality. Dorsey's tweet did not mention him.
In an earnings conference call in October, Dorsey spoke about "hiring and investing in talent" and the need for "bold rethinking".
Twitter may announce other executive changes, including the recruitment of a new chief marketing officer, on Monday, according to a source familiar with the matter. The company will announce two new board members soon, the person added.
Dorsey tweeted that Chief Operating Officer Adam Bain will take on additional responsibilities as a result of the departures, including revenue-related product teams and the HR team.
Chief Technical Officer Adam Messinger will handle the engineering team, he said.
Twitter, which has just over 300 million users, had its slowest user growth in 2015 and was eclipsed by photo-sharing app Instagram, owned by Facebook Inc, which surpassed 400 million users last year.