Twitter has announced that Dick Costolo is stepping down as chief executive, but will continue to serve on the board of directors.
The microblogging service's co-founder and chairman Jack Dorsey will take over as interim chief on 1 July until the board can find a long-term replacement.
The company has appointed a committee to conduct the search, led by independent director Peter Currie and including co-founder Evan Williams.
The committee will be assisted by an executive search firm to assist in conducting a global search, which will consider both internal and external candidates, the company said.
Costolo said in a statement he was proud of what the Twitter team has accomplished in the six years he has been at the company and that he looks forward to supporting Twitter in future, but gave no reason for stepping down as chief executive.
Commentators have noted that Costolo has come under increasing pressure from investors pushing for better growth in Twitter membership.
In a conference call with analysts to discuss the announcement, Costolo said he felt the continued scrutiny if he remained would be a “distraction” and of “no help to the company”.
Following the announcement that Costolo was stepping down, shares in the company increased by more than 7% in after-hours trading, the BBC reported.
In April, Twitter missed Wall Street's forecasts for revenue growth and posted a net loss of $162m. Its share price has declined by almost 30% since then, adding to investor concerns about growth.
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Some industry analysts have attributed Twitter’s slow growth, in part, to the fact that there has been little innovation to attract and retain users, but others say investor expectations are unrealistic.
Twitter reaffirmed its outlook for the second quarter of 2015, saying it continues to expect revenue to be in the range of $470m to $485m.
The company also announced that it plans to lift the 140-character limit for direct messages from July to make it more like other instant message and group chat services.
The move has been welcomed by businesses that use Twitter as part of their customer support service but found the 140-character limit a challenge.
The announcement comes two months after the app started allowing users to be able to receive direct messages from anyone. Previously, direct messaging could only happen between two Twitter users who followed each other.