By Tarmo Virki, European Technology Correspondent

(Reuters) - Fans of Lady Gaga or Justin Bieber looking for more than their 140-character tweets may soon be able to follow and hear their idols chatter over a new online service.

Voice microblogging service Bubbly, which allows people to send Twitter-like short sound messages, has grown to reach more than 12 million clients in Asia in just 18 months and plans to take the service global this year.

Bubbly, a service of startup Bubble Motion, currently has 75 staff based in Singapore.

It sends users a text message with a link to a short audio message from people they are following. The message is played back as a voice call.

To enable that, Bubble Motion has struck deals with local mobile phone operators for the service and for sharing revenues. This has created a strong revenue stream for the startup, which is almost profitable, said Chief Executive Thomas Clayton.

"With mobile operators acting as the gatekeepers to Asia's mass markets and the only viable means of doing microbilling to users, Bubble Motion's strategy of partnering with carriers has proved extremely fruitful," Clayton said.

In Japan -- where top followed people are soccer star Yasuhiko Okudera and idol group AKB Girls -- customers pay on average $43 a year for the service.

Over the past three months, Bubbly has launched on Vodafone in India, SoftBank Mobile in Japan and Indonesia's biggest mobile phone operator Telekomunikasi Selular (Telkomsel).

Bubble Motion plans to roll out applications for Apple's iPhone and Google's Android smartphone platform later this year and seeks to expand offerings from voice to text, photo and video in the future.

Adding text to the offering will put the service into direct rivalry with its own role model Twitter, but Clayton said so far the company has no rivals in offering distribution of large sound files -- they are too large for most of the telecom networks to handle.

And the audience so far is different.

On Twitter the most followed celebrities are Lady Gaga and Justin Bieber, but top celebrities on Bubbly include Bollywood stars Amitabh Bachchan and Lara Dutta, Indonesian singers and Japanese comedians.

Investors, including Sequoia Capital and Singapore Telecommunications, have put more than $40 million into the startup.

(Editing by Mike Nesbit)