Twitter has said that it now has 100 million active users and that the popularity of the microblogging site on mobile phones is surging.

Twitter chief executive Dick Costolo told reporters on Thursday that the company is now planning to expand its advertising space, and that it is in no hurry to undertake an initial public offering.

"We want to be able to remain independent, grow the business the way we want to, and not be beholden to public markets until we feel like we want to be," Costolo said.

Costolo also revealed that Twitter is "seeing tremendous growth on mobile."

He said that the number of users who log in at least once a month on the site, also known as ‘global active users’, has grown 82% from the start of the year, while usage on mobile devices grew 40% each quarter for the past year.

Costolo also announced that Twitter will allow adveritisements on ‘promoted tweets’ and that users will see those from companies that they do not follow.

"We now feel that based on the engagement rates we’re seeing … that we’re ready to expand this further," Costolo said.

He added, "It’s our firm belief that our advertising platform is the only revenue component that we need to have in the market in order to be a huge independent business."