That, they say, has forced them to highlight their cases through social media campaigns, marches and protests, such as the annual Missing and Murdered Indigenous People's March.

About 1,500 American Indian and Alaska Native missing persons have been recorded across the United States by the National Crime Information Center, and 2,700 homicide cases have been reported to the federal government's Uniform Crime Reporting Program.

The Justice Department has reported on some reservations, Native American women are murdered at a rate more than 10 times the national average.

But the existing data is not comprehensive, advocates say.

Annita Lucchesi, a descendant of the Cheyenne tribe and executive director of the research group Sovereign Bodies Institute, has been tabulating missing and murdered cases for the past few years.

The Indigenous-led group has documented 2,306 missing Native American women and girls in the US since the 1900s.

About 58% of those cases were homicides, the group said in a report last year.

In April, Interior Secretary Deb Haaland announced a new unit within Bureau of Indian Affairs that plans to tackle the decades-long crisis of missing and murdered Native Americans.

"Violence against Indigenous peoples is a crisis that has been underfunded for decades," Haaland said in an earlier statement.