UPDATE 1-Indonesia Indosat's H1 profit jumps 25 pct

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JAKARTA, Aug 28 (Reuters) - Indonesia's second-largest listed telecommunications company, PT Indosat Tbk (ISAT.JK), reported on Thursday a 24.9 percent rise in its first-half net profit, outperforming the earnings of its bigger rival Telkom over the period.

Indosat, which signed up 7.9 million new mobile phone users in the first half, close to its 8 million target, revised up its full year target for new users to 12 million.

The firm, which is around 40 percent owned by Qatar Telecom QTEL.QA, said in a statement net profit for the January-June period was 1.06 trillion rupiah ($115.8 million) compared to a revised figure of 845.1 billion rupiah for the previous year.

The result was in contrast to the country's top telecommunications firm, PT Telekomunkasi Indonesia Tbk (TLKM.JK) (Telkom), which reported a 5 percent fall in its first-half net profit, as a result of higher costs and a sharp fall in revenue per user.

Telkom controls 65 percent of PT Telekomunikasi Selular (Telkomsel), the country's largest mobile phone operator.

The number of mobile phone subscribers in Indonesia is expected to soar to 120 million by the end of 2008 from some 90 million last year, according to industry analysts and executives.

But the fast-growing mobile sector has attracted several new players, putting pressure on margins and revenue per users.

Indosat, which has a market capitalisation of $3.6 billion, booked a 14.9 percent rise in revenue in the first half.

Indosat's shares gained 0.83 percent to 6,050 rupiah after the the results were released, slightly behind a 1 percent rise in the broader market .JKSE. ($1 = 9,155 rupiah) (Reporting by Andreas Ismar, writing by Harry Suhartono, editing by Ed Davies)