By Robert Walker BBC, Rwanda

Regional conflicts have hampered counting in the past

The survey suggests the number of mountain gorillas has risen by 17% since 1989, despite insecurity and the threat from poachers.

In recent years there have been growing fears over their potential extinction.

However wildlife experts say gorilla numbers in the area remain critical at only a few hundred.

A remote range of volcanoes spanning the borders of Rwanda, Uganda and the Democratic Republic of Congo is home to one of the last surviving populations of mountain gorillas.

[This] is great news for us and good news for the rest of the world. The few additional gorilla individuals add to the genetic pool of the species Fidel Ruzigandekwe, Rwandan National Parks and Tourism Authority

During a decade of conflict in the region, gorillas have become easy prey for armed poachers.

To protect the remaining gorillas, national parks in the three countries launched an expensive programme of round-the-clock protection, and results from a new census suggest this has now paid off.

After weeks of tracking the gorillas through thick forests and deep ravines, conservationists found their number had increased by 17% since the last survey 15 years ago.

But despite the encouraging results, the mountain gorillas are still critically endangered. The survey found only 380 of them.