By Barbara Ortutay, Technology Writer

NEW YORK (AP) --

Twitter shares flew nearly 10 percent higher aftermarket, as the messaging service shrank losses and nearly doubled quarterly revenue by drawing more users and expanding its advertising offerings.

The number of new Twitter users was less than expected, but Twitter showed that it's able to make money from the users it does have.

"We have a number of projects under way to grow our user base and provide a compelling valuable experience to anyone in the world whether they have a Twitter account or not," CEO Dick Costolo said in a conference call with investors. This includes strengthening the core Twitter service, making it easier to join and use and building new applications and services.

Twitter's user growth lags other popular social networks. The company had 288 million monthly users at the end of the quarter, up 20 percent from a year earlier. But the pace of growth slowed in the fourth quarter, something Twitter attributed to changes in the way third-party apps integrate Twitter. However, CEO Dick Costolo said Twitter expects to add a similar number of net users in the first quarter as it did in each of the first three quarters of 2014.

By comparison, LinkedIn Corp. on Thursday reported 347 million users through the end of December. The Facebook-owned photo sharing app Instagram, meanwhile, recently surpassed 300 million users. None come close to Facebook, however, with its 1.39 billion members.

"Twitter's biggest challenge is to prove it can win and retain new users. Just 18 months ago Twitter was clearly the #2 consumer social network, but now it appears to have tumbled into fourth place," Forrester Research analyst Nate Elliott said in an e-mail. "Relative newcomers like Instagram and Pinterest have spent the last year collecting more and more new users. But Twitter has acquired only a modest number of new users in the past year, and its engagement rate per user actually went down slightly last quarter."

At the same time, Elliott noted that Twitter's bright spot is that it's getting better at making money from the users it does have.

The San Francisco-based company was still privately held for part of the year-ago quarter — it went public in November 2013. For the final three months of 2014 it had losses of $125.4 million, or 20 cents per share, down sharply from a loss of $511.5 million, or $1.41 per share, a year earlier. Excluding one-time items, Twitter earned $79.3 million, or 12 cents per share — double the 6 cents expected by analysts, according to FactSet.

Revenue surged to $479.1 million from $242.7 million, also topping analysts' average estimate of $453.8 million. Mobile advertising revenue amounted to 88 percent of Twitter's total ad revenue. International revenue was $164 million, or about a third of the quarter's total ad revenue. That's well over double last year's as the company worked to expand overseas.

For the current quarter, Twitter is forecasting revenue of $440 million to $450 million. The midpoint is slightly below analysts' $449.5 million estimate.

Twitter's stock had closed before the report at $41.26, a decline of 37.5 percent over the past year amid concerns about its ability to broaden its audience. After the results, the stock jumped $3.79, or 9.2 percent, to $45.05 in extended trading.

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