Twitter Inc. Chief Executive Dick Costolo said the microblogging service is “already making money,” but he did not immediately clarify whether he was referring to revenue or profit.

Costolo made his comments in a webcast keynote address at Mobile World Congress in Barcelona, but a subsequent Q&A period was not streamed on the Internet.

The San Francisco-based microblogging service has emerged as one of the key drivers of the social media trend, but Costolo acknowledged that Twitter must do a better job of getting its users engaged with each other, a step that will induce them to use the service more.

He said the popular microblogging service’s mission statement is to “instantly connect people everywhere to what’s most meaningful to them.”

He said Twitter users are generating more than 130 million tweets per day, and the service is growing at a “ridiculous rate.”

Costolo noted that more and more people are using the service to share common events, such as TV shows, live sporting events or mass celebrations like New Years Eve in Japan, where they recently set a record of 6,000 tweets per second.

He also revealed that 40 percent of all tweets are created on by people using mobile devices.

The Wall Street Journal reported last week that a number of suitors, including Google Inc.  and Facebook Inc., have held low-level talks with Twitter to explore a possible acquisition.

The article said the discussions have produced an estimated valuation of $8 billion to $10 billion for Twitter, which lost money on $45 million in revenue in 2010. It was estimated Twitter will generate between $100 million and $110 million in revenue this year. Twitter declined comment for that story.

With more than 200 million registered users, the company added advertising last year to turn itself into a profitable business. The WSJ said one of Twitter’s ad services, called Promoted Trends, has been selling out  every day, while two other ad formats, Promoted Tweets and Promoted Accounts, also were doing brisk business.