South Korea was the world's most advanced Internet and telecommunications economy in 2010, with high levels of access, usage and skills, while high-speed Web access remained unaffordable in many low-income countries, the United Nations said on Thursday.

Mobile subscriptions grew 20 percent over the past year to more than 5 billion, with penetration of over 100 percent, or more than one mobile device per person, in developed countries and 70 percent in developing countries at the end of 2010.

Mobile broadband Internet access mushroomed, especially in developing countries where fixed broadband access is scarce, the UN's International Telecommunication Union found in its annual information and communication technology (ICT) report.

But with mobile broadband prices for a monthly subscription of 1 gigabyte costing more than 10 percent of monthly income in countries such as India, Mali, Kenya and Brazil, high-speed Internet access remained unattainable for many.

The 'mobile miracle' is putting ICT services within reach of even the most disadvantaged people and communities. Our challenge now is to replicate that success in broadband, the ITU's Secretary-General Hamadoun Toure said in the report.

The Internet was used by just 21 percent of the population in the developing world, compared with almost 70 percent in developed countries, the ITU said.

Fixed-line broadband prices dropped by 52 percent globally between 2008 and 2010, but in Africa still cost on average almost three times monthly income. In developed countries, ICT services cost under 1.5 percent of monthly income.

Sweden, Iceland, Denmark and Finland were the next most advanced ICT countries after South Korea, according to the ITU's development index. The United States was 17th, and China -- with the world's most Internet users -- 80th.

(Reporting by Georgina Prodhan in London, editing by Gerald E. McCormick)

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