Fast-growing economies Brazil, Russia, India, China and Indonesia will drive a "massive digital revolution" in coming years as disposable incomes increase, a study released Wednesday suggested.

The Boston Consulting Group said more than 610 million people in the "BRICI" markets currently use the Internet regularly but that will grow to 1.2 billion by 2015 -- over three times more than the United States and Japan combined.

Annual growth will be between nine to 20 percent, driven predominantly by young users who "will form the digital-market eco-systems that will be in place for generations to come", the US-based management consulting firm said.

"Right now, 60 percent of BRICI Internet users are under the age of 35," said the report, entitled "The Internet's New Billion".

"As they earn even higher incomes and develop more complex online needs, there will be a colossal opportunity for digital companies to monetise services and products.

"Those companies that manage to do so will reap the tremendous benefits of this massive digital revolution."

The study highlighted wide-ranging differences in the ownership of personal computers in the five countries, from five percent in India and Indonesia to 20 percent in China and about 32 percent in Brazil and Russia.

But while it suggested that Brazil and Russia would see a far greater take-up of PCs in the next five years, Internet users in other countries could skip the PC ownership stage and move straight into the mobile Internet market.

Mobile phone ownership is already high in BRICI countries, making web-enabled smartphones a potential growth area as networks expand.