Human skulls taken from Namibia by Germany during the colonial period have finally been returned after more than 100 years, but now historians and activists demand that Germany pay reparations for the slaughter of more than 60,000 people.

Twenty skulls brought to Germany ago for now-discredited racial experiments are back home, but people whose ancestors were mercilessly decimated when they rebelled against German colonisers insist they still suffer injustices 100 years later.

The skulls were first ordered around 1903 by Eugen Fischer, a racist German anthropologist who believed he could prove that blacks were inferior to whites by measurements of their cranium.

European colonisation in Africa led to various massacres, many still brushed aside or not formally acknowledged by the former colonial powers, but the genocide committed by German soldiers in what they called South West Africa is seen by some historians as a precursor to the Nazi Holocaust of the Jews.

The Herero people, about 85,000 strong, were successful and powerful herders when German colonisation in their country began in the 1890s.

After they revolted against the colonisers, they were decimated and within three years 85 per cent were dead, their land and cattle stolen, with many bodies beheaded. German troops also made the Herero dig up the graves of relatives and ancestors.

The Herero now make up only some 10 per cent of Namibia's population of 2.1 million, but they say many of them are dispossessed of their ancestors' lands, much still owned by descendants of the white settlers who seized it more than 100 years ago.

As tensions rise and the Herero demand justice, they now threaten to attack the farms owned by the descendants of the white settlers.

"If something is not done, we cannot guarantee that you will not see the same kind of land grabs that you see in Zimbabwe," warned Hoze Riruako, a university professor and senior adviser to the paramount chief of the Herero.

In 2004, Germany apologised and acknowledged its "political and moral responsibility for the past and colonial guilt," but it has never admitted committing a genocide. It will send large sums of aid money but refuses to pay reparations.

The arrival of the skulls drew a large crowd as people dressed in traditional garb, warriors on horseback and women ululating welcomed the remnants of their ancestors.

"We are ready for battle! We are going to fight!" chanted Herero warriors in military uniform as their leader led a cleansing ceremony.

The Herero are also turning to their own government, which they also blame for contributing to inequalities.

Veneruru Korumbo, head of the Herero Youth League, says the community is heavily affected by unemployment and struggles for access to education while the government uses international development aid to benefit the majority tribe, the Ovambo.

Phil ya Nangoloh, head of the Namibian Rights and Responsibilities human rights group, said: "Areas that are populated by the Hereros are less developed, schools and hospitals are dilapidated, you have to cover long distances to reach them, and the roads are not tarred as they are in northern areas, where the government comes from."

"It's not just the Hereros, but all other ethnic groups that are being marginalised," he added.

Namibia is rich in natural resources such as diamonds, uranium and other minerals, and also exports beef and fish, but people still struggling with poverty and inequality.

While the poorest, who make up 20 per cent of the population, earn only 1.4 per cent of national income, the richest 20 per cent of the population enjoys nearly 80 per cent.