Africans are buying mobile phones at a world record rate, with take-up soaring by 550% in five years, research shows.

"The mobile phone revolution continues," says a UN report charting the phenomenon that has transformed commerce, healthcare and social lives across the planet. Mobile subscriptions in Africa rose from 54m to almost 350m between 2003 and 2008, the quickest growth in the world. The global total reached 4bn at the end of last year and, although growth was down on the previous year, it remained close to 20%.

On average there are now 60 mobile subscriptions for every 100 people in the world. In developing countries, the figure stands at 48 – more than eight times the level of penetration in 2000.

In Africa, average penetration stands at more than a third of the population, and in north Africa it is almost two-thirds. Gabon, the Seychelles and South Africa now boast almost 100% penetration. Only five African countries – Burundi, Djibouti, Eritrea, Ethiopia and Somalia – still have a penetration of less than 10 per 100 inhabitants.

Uganda, the first African country to have more mobiles than fixed telephones, is cited as an example of cultural and economic transformation. Penetration has risen from 0.2% in 1995 to 23% in 2008, with operators making huge investments in infrastructure, particularly in rural areas. Given their low incomes, only about a quarter of Ugandans have a mobile subscription, but street vendors offer mobile access on a per-call basis. They also invite those without access to electricity to charge their phones using car batteries.

Popular mobile services include money transfers, allowing people without bank accounts to send money by text message. Many farmers use mobiles to trade and check market prices.

Growth is expected to remain robust, says the Information Economy Report, published today by the UN Conference on Trade and Development (Unctad). The regional mobile operator MTN forecasts an average mobile penetration of 80% by 2012 in its 15 African markets.

But the main barrier to further expansion is cumbersome regulatory frameworks, the report adds. "Countries with similar economic circumstances but with a liberalised market generally show higher penetration rates," it says. "Taxes can also act as a barrier, particularly import duties on handsets or special mobile communications surcharges. The mobile industry has been seen as a cash cow in some countries."

The share of the population covered by a mobile signal stood at 76% in developing countries in 2006, including 61% in rural areas. In sub-Saharan Africa, closer to half the population was covered, including 42% in rural areas.

The income barrier to mobile ownership has been reduced thanks to more efficient network equipment and affordable handsets. But the report says that to expand coverage into rural and remote areas, government support may be required. "Rural areas in some countries are often economically unattractive for operators to invest in. This is usually not due to a lack of demand but rather to economies of scale."

Mobiles have come as a blessing to those who never had access to landlines because of poor infrastructure. At the end of 2007, there were eight times as many mobile phones as fixed lines in the least developed countries. The number of fixed lines in the world has essentially been frozen around 1.2bn since 2006 and saw a slight decline in 2008.

But a "digital divide" persists in terms of internet access. Australia, a country with 21 million inhabitants, has more broadband subscribers than the whole of Africa. There is also a huge gap in terms of broadband speed. The report warns: "Urgent attention is needed to address this situation and bring the continent more meaningfully online."

Other developing regions often boast a broadband penetration 10 times higher than in Africa, where Algeria, Egypt, Morocco, South Africa, and Tunisia account for 90% of all subscriptions. Broadband access in Burkina Faso, the Central African Republic and Swaziland is the most expensive in the world, costing more than $1,300 (£780) a month.

Torbjörn Fredriksson, head of the ICT analysis section at Unctad, said: "Even though broadband usage is disappointing, there is a good story to tell in Africa about the astonishing growth of mobile telephony, despite the financial crisis.

"We expect this progress to remain robust as the income barrier to mobile ownership continues to drop, thanks to liberalisation, more efficient network equipment and more affordable handsets. This is because operators have made significant investments in infrastructure across the continent. And there appears to be continued interest among investors in expanding and upgrading these networks in Africa."

He added: "This report stresses that despite the positive trends in mobile telecommunications in Africa, there is no room for complacency. A long-unfinished agenda must be addressed to create a truly inclusive information society for all."

The report also found that at the end of 2008 there were an estimated 1.4bn internet users around the world. The growth rate of 15% was slightly lower than in 2007. In developing countries, the number of users grew by a quarter and such countries now account for more than half the world's internet users. But while more than half of the developed world population is now online, the corresponding share is only 15% in developing economies and 17% in "transition" economies.

China hosted the biggest number of users (298 million), followed by the United States (191 million) and Japan (88 million). A little over one fifth of the world's population used the internet in 2008.