Twitter's User Growth Slows to a Crawl'This is unacceptable and we're not happy about it,' said Twitter's interim CEO and co-founder Jack Dorsey.

Twitter Inc's quarterly earnings and revenue blew past expectations, but its monthly average user number grew at its slowest pace since it went public in 2013, and its shares fell about 7 percent after hours.

"We do not expect to see sustained meaningful growth in maus until we start to reach the mass market," Chief Financial Officer Anthony Noto said, referring to monthly active users of the microblogging service.

The company said on Tuesday it had 304 million core users in the second quarter, up from 302 million in the prior quarter.

"This is unacceptable and we're not happy about it," Jack Dorsey, who stepped in as interim chief executive on July 1, said on a call with analysts.

Twitter said revenue rose 61 percent to $502.4 million. Excluding the impact of a strong dollar, revenue rose 68 percent.

The company's net loss narrowed to $136.7 million, or 21 cents per share, in the second quarter ended June 30 from $144.6 million, or 24 cents per share, a year earlier.

Excluding items, Twitter earned 7 cents per share.

Analysts on average had expected Twitter to earn 4 cents per share on revenue of $481.3 million, according to Thomson Reuters I/B/E/S.

Twitter estimated full-year revenue of $2.20 billion-$2.27 billion, up from its previous forecast of $2.17 billion-$2.27 billion.

Last quarter, it lowered its full-year revenue forecast after weak demand for its direct-response ads, which prompt users to take actions such as clicking on a link to an advertiser's website or downloading an app.

Twitter is also in the midst of a management change after Chief Executive Dick Costolo abruptly announced in June that he was stepping down.

After the bell, Twitter shares extended losses and were down about 7 percent at around $34, after closing at $36.54 on the New York Stock Exchange.

(Reporting by Devika Krishna Kumar in Bengaluru and Yasmeen Abutaleb in San Francisco; Editing by Sriraj Kalluvila andRichard Chang)