With mobile phone penetration in the region's wealthier nations at 70 percent and above, operators such as Singapore Telecomm-unications Ltd, South Korea's SK Telecom Co and Hong Kong-based Hutchison Telecommunications International Ltd are spending billions of dollars entering new markets.

The biggest prizes are in countries with large populations and very low mobile usage such as Indonesia, India and China.

"There are big growth opportunities out there to compensate for the slowing growth story in the domestic market," said Yang Jong-in, an analyst at Korea Investment & Securities.

"But risks exist as well and it's not just low penetration rate operators have to consider. They have to decide level of income and competition in the target market, and need a strong case to persuade shareholders preferring more dividend to risky investments." Most of the big regional operators currently trade cheaply as investors shun the sector amid weakening growth momentum.

SingTel trades around 13.4 times its forecast annual earnings, Telekom Malaysia around 18.9 and SK Telecom around 8.6, compared with an average for the MSCI AsiaPacific telecoms sector of around 49.8.

India is attracting the most overseas attention, and growth rates have soared to 2.5 million new subscribers per month, helped by the world's cheapest call rates of 1-2 US cents a minute and the opening up of the sector to foreign competition.

"The mobile markets in many South Asian countries offer immense business potential due to their very low penetration rates," said peter Heng, a spokesman for SingTel.

Asia's fifth-largest phone firm by market value derives about 75 percent of revenue overseas after investing $11 billion in recent years, with its tentacles stretching to India, Australia, the Philippines, Indonesia and Bangladesh.