Indian googler

Twitter on Monday announced that Dick Costolo has become its chief executive officer (CEO), replacing Evan Williams, co-founder of the micro-blogging service.

Costolo, a Google veteran who joined Twitter last year as its chief operating officer (COO), took over the new role of CEO effective immediately.

During his year at Twitter, Costolo "has been a critical leader in devising and executing our revenue efforts, while simultaneously and effectively making the trains run on time in the office," Williams said in a post on Twitter's blog announcing the hand-over of the reigns.

"Starting today, I'll be completely focused on product strategy, " said Williams, who co-founded Twitter in 2006 with Jack Dorsey and Biz Stone.

Twitter, which allows users to post status updates with a 140- character limits, has witnessed repaid growth in user base since its launch.

Williams said there are 300 people now working at Twitter, compared to about 20 when he took the CEO job two years ago.

"Back then, people were creating about 1.25 million tweets a day -- compared to 90 million today. In those same two years, we grew from 3 million registered users to more than 165 million today," he noted.