One of the first and most comprehensive studies of the media in sub-Saharan Africa has revealed massive growth in the industry over the past five years, with the emergence of private and community radio stations and an explosion in the use of mobile telephones. However, the study says African media are not yet strong enough or independent enough to fulfill the role of the fourth estate. Correspondent Scott Bobb reports from our Southern Africa bureau in Johannesburg.

A survey by the African Media Development Initiative released Monday says the media on the continent have undergone considerable growth and change in the past five years.

The director of one of the sponsors of the study, Steven King of the B.B.C. World Service Trust, says this is due to democratization, globalization and economic growth.

"The private media has grown very substantially and that's largely due to liberalization. We've also seen a large growth in some countries in community media stations," said King.

The study was conducted by the Trust, Nigeria's Ahmadu Bello University, South Africa's Rhodes University and a network of researchers in 17 African countries. They interviewed more than 300 leaders in media, government, academia and related fields.

King says the researchers found a surprising consensus on the state of the media in sub-Saharan Africa.

"Radio is still the dominant media although television is growing fast," he said. "And also another significant but not surprising statistic is the growth of mobile telephony and also in some countries a massive uptake of access to internet."

He says newspapers often do not reach audiences in rural areas and internet access, while growing, is still limited. For example, two-thirds of all internet users live in Nigeria or South Africa.

However, the report says the media in Africa face many challenges. They are neither strong enough nor independent enough to fulfill their role as the fourth pillar of democracy along with the executive, legislative and judicial branches of government.

One of the research leaders, Gerry Power, says state-owned broadcasters tend to dominate but they are not independent.

He said, "In many of these countries, despite the liberalization, they tend still to serve the needs of the ruling government and tend to be the mouthpiece of the ruling party."

The study says that laws guaranteeing the freedom of the media are lacking in many countries and is not implemented in many where they do exist.

In addition, African media suffer from low technical standards, low professional standards and funding shortages.

King says, however, that vigorous and independent media are vital in the struggle to end poverty and promote good governance.

"In a globalized world people succeed and economic growth happens because of a more liberalized and globalized access to information. And to deny that to many people in the development world is a real brake on development," he said.

The study recommends new funding schemes to ensure financial sustainability, more and better coordinated training programs and the implementation of laws that protect the media from interference by government and wealthy private interests.