Oglala Sioux Tribe President Frank Star Comes Out is demanding the release of three enrolled tribal citizens believed to be held by ICE in Minnesota.

The detentions were reported after four Oglala Sioux men experiencing homelessness were taken into custody last week in south Minneapolis while living under a bridge near Little Earth, a long-standing Indigenous housing community.

AP News reported three of the four men were transferred to an ICE detention centre at Fort Snelling but federal authorities have not publicly confirmed their custody.

A memorandum sent to federal authorities outlines the tribe's position that ICE has no authority to detain tribally enrolled citizens under immigration jurisdiction.

"'The Oglala Sioux Tribe's memorandum makes clear that 'tribal citizens are not aliens' and are 'categorically outside immigration jurisdiction,'" Mr Star Comes Out said.

"Enrolled tribal members are citizens of the United States by statute and citizens of the Oglala Sioux Nation by treaty."

AP News reported the tribe was given only the first names of the men when it sought information from Homeland Security.

The report said DHS refused to provide further details unless the tribe "entered into an immigration agreement with ICE", which Mr Star Comes Out rejected.

Fort Snelling has become a central point of concern due to its historical significance for Indigenous people in Minnesota.

Nick Estes, a University of Minnesota professor and member of the Lower Brule Sioux Tribe, described the location as a continuation of state power targeting Indigenous communities.

"It has this really notorious anti-Indigenous, specifically anti-Dakota, history," Mr Estes said.

"It's kind of like a continuation on the monopoly of violence from the military outpost to the ICE facility.

Mr Star Comes Out said the symbolism of holding Lakota citizens at Fort Snelling was impossible to ignore.

"The irony is not lost on us," said Mr Star Comes Out.

"Lakota citizens who are reported to be held at Fort Snelling - a site forever tied to the Dakota 38+2 - underscores why federal treaty obligations and federal accountability matter today, not just in history."

Across Minneapolis, Indigenous organisations have stepped up street-level support, urging tribal citizens to carry identification and stay calm during encounters.

"I never thought that I'd have my tribal ID hanging around my neck, but I do," said Mary LaGarde, executive director of the Minneapolis American Indian Center.

"So, it's just important that they have proper identification on them and not to panic."

MPR News reported the Oglala Sioux Tribal enrollment office will be on site at the Minneapolis American Indian Center on Friday to assist with enrolment verification and documentation.

A news conference is scheduled for Friday afternoon as the tribe continues pushing for answers and the release of the remaining men.