Drone footage of the clash has been widely shared on social media. (Digital Smoke Signals Facebook)

Drone footage of the clash has been widely shared on social media. (Digital Smoke Signals Facebook) Source: Digital Smoke Signals Facebook

Police have used tear gas and water cannons against hundreds of protesters, in the latest violent clash between law enforcement and activists over the Dakota Access Pipeline.

An estimated 400 protesters mounted the Backwater Bridge just north of Cannon Ball, North Dakota, and attempted to force their way past police in what the Morton County Sheriff's Department initially described as an "ongoing riot."

Police fired volleys of tear gas at the protesters to prevent them from crossing the bridge. Law enforcement also sprayed protesters with water in sub-freezing temperatures, and fired rubber bullets, injuring some in the crowd.

The independent TYT (The Young Turks) News Network, have posted graphic footage of the events. The video has been watched over 2.5 million times.

"It is below freezing right now and the Morton County Sheriff's Department is using a water cannon on our people - that is an excessive and potentially deadly use of force," said Dallas Goldtooth, a spokesman for the Indigenous Environmental Network, one of the organisations involved in protests.

The protest was latest in a series of demonstrations against the Dakota Access Pipeline that Native American activists and environmentalists say threatens water resources and sacred tribal lands.

The Dakota Access project has drawn steady opposition from activists since the summer, led by the Standing Rock Sioux tribe, whose tribal lands are adjacent to the pipeline.

Supporters of the pipeline, owned by Energy Transfer Partners, said the project offers the most direct route for taking shale oil from North Dakota to Gulf Coast refineries and would be safer than road or rail transportation.

Completion of the pipeline, set to run 1,885 km from North Dakota to Illinois, was delayed in September so federal authorities can re-examine permits.