Cannon Ball, United States – Thousands of Native Americans have been camping out in North Dakota since April to protest against a pipeline that is meant to cross sacred burial grounds and the Missouri river – the main water source for the Standing Rock Sioux Tribe.

Last week, some protesters moved their camp directly in the path of the proposed pipeline as construction nears the river, but on Thursday morning, police descended on the camp with a show of force not yet seen in the months of peaceful protests.

Clad in riot gear and backed by armoured vehicles, the police cleared the protest camp, using sound cannons, pepper spray, taser guns, and shotguns said to contain beanbags against the protesters.

More than 100 people were arrested, including elders praying peacefully in the roadway, according to the Morton County Sheriff Department.

The department said a protester fired three shots at police, but Al Jazeera could not independently verify this allegation.

Some protesters shouted at police, built and lit fire to barricades, and a few threw water bottles and logs at the officers as tensions rose, but most remained nonviolent as protest leaders urged colleagues to fall back from the superior government force.

Police continued to march south into the night, blocked only by a burning barricade set up by protesters as dusk fell.