By Cordelia Hebblethwaite

BBC World Service

The search for Scotland's Loch Ness Monster is world famous. Far less well-known is the hunt for a similar creature, Mokele-mbembe, which is reputed to live in the remote north of Congo-Brazzaville. But how strong is the evidence?

"I checked maps, and the data on the maps was white. It said, 'insufficient data to delineate terrain'. Well that got me!" says Dr Roy Mackal, a retired biologist from the University of Chicago.

"It's the end of the world. It gives you a feeling of a surviving prehistoric time."

In the 1980s, Dr Mackal led two expedition teams to the vast Likouala swamp and rainforest area of the Congo which is inhabited by pygmies, on the hunt for this mystery creature - Africa's version of Scotland's Loch Ness Monster.

The Mokele-mbembe is reputed to be a large reptile-like creature, with a long neck, and long tail.

Despite being a herbivore, it is said to roar aggressively if approached by humans. Some say it has a single horn, which it uses to kill elephants.

Many a Western explorer over the years has been gripped by the tantalising possibility that they could discover a creature - a formidable one at that - that has remained, as yet, unknown to science.

To date, there have been more than 50 expeditions to the region, but no scientific evidence, unless you include the large claw-shaped footprint recorded by a French missionary in 1776, and by a number of others since.

The only photographic images have been so fuzzy, they prove nothing.

But there is no shortage of eyewitness reports.

"I was in a boat on the river when I saw Mokele-mbembe. He began to chase us. Mokele-mbembe rose out of the water," one man told the BBC. "We ran, or he would have killed us."

Edited by Brenda Booth