Activists are opposing an oil pipeline project which threatens local water supplies. Police have responded with a millitarised use of force.
The Native American Standing Rock tribe and other activists vowed on Friday to continue their fight against a multibillion-dollar oil pipeline project in North Dakota, a day after police arrested 141 of their members.
In a statement, Dave Archambault II, the tribe's chairman, said, "We won't step down from this fight... This is about our water, our rights, and our dignity as human beings."
The project has drawn opposition from activists, including a growing list of celebrities, who say it threatens local water supplies and sacred tribal sites.
Meanwhile, Amnesty International has sent a delegation of human rights observers to monitor the tense situation as they expressed alarm at the militarised use of force by local police, according to a recent press release.
"People here just want to stand up for the rights of Indigenous people and protect their natural resources. These people should not be treated like the enemy," said Eric Ferrero, director of communications for AIUSA.
"Police must keep the peace using minimal force appropriate to the situation. Confronting men, women, and children while outfitted in gear more suited for the battlefield is a disproportionate response."
Activists have been protesting for several months, and a total of 411 protesters have been arrested since August 10, the sheriff's department said.
Thursday's arrests came at the site of the $3.8 billion Dakota Access pipeline, when dozens of riot police swept through a protester camp on private land using pepper spray, bean bag rounds and an audio cannon against demonstrators who refused to leave.
Amid the protests, the US government halted construction on part of the pipeline in September.
He affected area includes land under Lake Oahe, a large reservoir on the Missouri River where the line was supposed to cross.
Meanwhile, opposition to the pipeline continues to gather the backing of celebrities.
Among the actors who have already lent their voices to the cause are Shailene Woodley, Susan Sarandon and Mark Ruffalo.
On Thursday, Australian actor Chris Hemsworth showed his solidarity with demonstrators in an Instagram post.
Standing with those who are fighting to protect their sacred land and water. #nodapl #waterislife #mniwiconi @taikawaititi I would also like to take this opportunity to raise something that has been bothering me for sometime. Last New Year's Eve I was at a "Lone Ranger" themed party where some of us, myself included, wore the traditional dress of First Nations people. I was stupidly unaware of the offence this may have caused and the sensitivity around this issue. I sincerely and unreservedly apologise to all First Nations people for this thoughtless action. I now appreciate that there is a great need for a deeper understanding of the complex and extensive issues facing indigenous communities. I hope that in highlighting my own ignorance I can help in some small way.