Two indigenous groups in Namibia have filed a lawsuit against Germany accusing it of genocide committed by colonial rulers more than a century ago.

The suit was filed in New York on Thursday by the Ovaherero and Nama people who seek compensation for what their ancestors suffered. They also want to be included in talks between Germany and Namibia on the issue.

The two countries have been in discussions about a joint declaration on massacres carried out by German settlers during the 1900s, although Berlin has repeatedly refused to acknowledge that genocide occurred or to pay compensation.

READ MORE: Genocide negotiations reopen colonial wounds in Namibia

The dispute goes back to the late 19th and early 20th century when then South West Africa, now known as Namibia, was a German colony.

The suit alleges from 1885 to 1903 about one-quarter of Ovaherero and Nama lands were taken without compensation by German settlers, with the explicit consent of German colonial authorities.

It also claims German authorities turned a blind eye to rapes by colonists of Ovaherero and Nama women and girls, and the use of forced labour.

Tensions boiled over in early 1904 when the Ovaherero rose up, followed by the Nama - a rebellion crushed by German imperial troops.

The lawsuit alleges that as many 100,000 Ovaherero and Nama people died in a campaign of annihilation led by German General Lothar von Trotha.

Activists have presented correspondence from the German general to prove the genocide.

Published documents also show victims were placed in forced labour camps and possibly experimented on.

The lawsuit was filed under Alien Tort Statute, which does not usually cover foreign conduct unless it somehow "touched" the United States.

A US-based non-profit group, Association of the Ovaherero Genocide, is one of the plaintiffs, along with Vekuii Rukoro, identified as the chief of the Ovaherero people, and David Frederick, chief and chairman of the Nama Traditional Authorities Association.