More than 20 traditional chiefs of Namibia's nomadic Himba people have appealed to the United Nations to stop construction of a huge dam in their area, human rights activists said Thursday.

The Himba say that generations of graves would be flooded by the mooted 1,700-gigawatt hydroelectric dam. The Himba worry their ancestors will be angered and could react badly, causing havoc in their lives.

"We have not been consulted and we would lose our graveyards and sacred places, flooded by the dam," said a declaration signed by 26 Himba chiefs, released by local human rights campaigners NamRights.

"We will never give our consent to have our river blocked... our environment destroyed and our land taken away from us."

NamRights director Phil ya Nangoloh told reporters he had submitted the declaration to the Namibian government and to the AU Commission on Human and People's Rights.

The Himba argue the dam violates their rights under the UN Declaration on the Rights of Indigenous Peoples, which Namibia has adopted.

Chief Hikumine Kapika also invited UN special rapporteur on indigenous rights James Anaya to visit the affected Himba communities.

In a sparsely populated country of two million people, about 18,000 Himbas live in northwestern Namibia, with another 9,000 just across the border with Angola.

Their ancestors migrated from the Great Lakes region of central Africa about 200 years ago, and they have survived with their traditions despite wars and droughts.