Sioux tribes in the US state of South Dakota are refusing to remove coronavirus checkpoints they set up on roads which pass through their land.

South Dakota Governor Kristi Noem wrote to several tribal leaders last week saying the checkpoints were illegal.

But the Sioux say they are the only way of making sure the virus does not enter their reservations.

Their limited healthcare facilities would not be able to cope with an outbreak, they say.

At present, people are only allowed to enter the reservations for essential business if they have not travelled from a Covid-19 hotspot.

They must also complete a health questionnaire before doing so.

Ms Noem is threatening to take the two tribes - the Oglala Sioux and the Cheyenne River Sioux tribes - to federal court if they do not comply.

In a letter sent to their representatives on Friday, she demanded the checkpoints be removed.

"The checkpoints on state and US highways are not legal, and if they don't come down, the state will take the matter to federal court, as Governor Noem noted in her Friday letter," her senior adviser and policy director, Maggie Seidel, said in an email sent to the local Argus Leader newspaper on Sunday.