Twitter boss Dick Costolo quits
The chief executive of Twitter has quit the social network amid pressure from shareholders over the site's user numbers.
Dick Costolo announced that he had decided to leave the California-based company at the beginning of July, and will be replaced as interim chief executive by Twitter co-founder Jack Dorsey.
The social network has around 300 million users globally, some way behind rival Facebook's 1.3 billion active users. The number of those signing up to Twitter in the last year has been slower than hoped, reportedly leading to some investors to call for a change.
Facebook-owned WhatsApp Messenger, Facebook Messenger and Instagram all also have similar user numbers to Twitter, and Mr Costolo has been under pressure to close the gap with Facebook, and improve Twitter's market share in the social networking world. Already this year the site has launched a live video streaming app, Periscope, as part of the attempts to lure new users.
Mr Costolo's departure also comes just months after he admitted that Twitter "sucks" at dealing with abusive behaviour and content, which in the past has seen a host of high-profile users quit the social network over abuse they received.
He said at the time that he took personal responsibility.
In a statement announcing his departure, he said: "I am tremendously proud of the Twitter team and all that the team has accomplished together during my six years with the company.
"We have great leaders who work well together and a clear strategy that informs our objectives and priorities."
Twitter stock rose by more than 7% in the wake of Mr Costolo's announcement.
He added: "I am deeply appreciative of the confidence the board, the management team and the employees have placed in me over the years, and I look forward to supporting Twitter however I can going forward."
Twitter's board of d irectors named Jack Dorsey, the site's co-founder and chairman, to serve as interim chief executive while a replacement is found.
Mr Costolo will continue to serve on Twitter's board of d irectors, the company said.
He said of his interim successor: " There is no-one better than Jack Dorsey to lead Twitter during this transition.
"He has a profound understanding of the product and Twitter's mission in the world as well as a great relationship with Twitter's leadership team."
Mr Dorsey said: "The future belongs to Twitter thanks in large part to Dick Costolo's dedication and vision. Dick has put a world-class team in place and created a great foundation from which Twitter can continue to change the world and grow."
There have been reports suggesting Twitter could be the subject of a buy-out, with Google having been linked with a move for the social network in April.