About 40 people gathered in south London Monday afternoon for a peaceful demonstration to show support for those at Standing Rock in North Dakota.
Starting around 12 p.m., supporters gathered at the Wellington Road 401 overpass.
London police closed the road to both north and southbound traffic.
The protest is expected to last about an hour.
The U.S. Army Corps of Engineers has refused to grant permission for the Dakota Access oil pipeline to cross under a Missouri River reservoir in North Dakota.
Protestors say it's a major victory in their push to reroute construction of the pipeline that they say could harm Standing Rock Sioux cultural sites and drinking water supply.
Pipeline developer Energy Transfer Partners says the 1,200-mile pipeline through the Dakotas, Iowa and Illinois will be safe and that the Corps' decision is politically motivated.
The Corps on Sunday denied an easement for a pipeline crossing beneath Lake Oahe, a Missouri River reservoir and the source of drinking water for the nearby Standing Rock Reservation.
Assistant Secretary for Civil Works Jo-Ellen Darcy said her decision was based on the need to consider alternative routes.
With files from the Associated Press
