Native American protesters were reportedly attacked by security guards at the construction site of a multi-billion dollar oil pipeline in North Dakota.

Members of the Standing Rock Sioux tribe launched a campaign against the construction of the Dakota Access pipeline in Cannon Ball after tribal leaders alleged the construction project has destroyed several Native American cultural sites and burial grounds.

Tribe leaders have challenged the permits in a federal court, and a judge is expected to decide whether or not the construction can be halted on 9 September.

The Army Corps of Engineers granted permits the Dallas-based Energy Transfer Partners.The project is estimated to cost $3.8bn and will carry some 500,000 barrels of crude per day from North Dakota to Illinois, according to NBC News.

During the Saturday protest, at least six people, including a child, are said to have received bites from guard dogs belonging to a private security company at the site, according to tribe spokesperson Steve Sitting Bear. He said at least 30 demonstrators were hit with pepper-spray.

Police had not arrived at the scene before the reported attacks.

Morton County Sheriff’s Office spokesperson Donnell Preskey said law enforcement received no reports of dog bites, but said that four security guards and two guard dogs were injuring during the confrontation.

Independent news channel Democracy Now was on the scene of the protest and captured images of tribespeople with arms bloodied from apparent bites from the canines. Video showed dogs lunging at activists as they marched through mounds of dirt created by the preliminary construction.

Members of the Standing Rock Sioux tribe fear the construction will also taint the area’s drinking water supply, in addition to concerns about recently discovered sacred sites in the area.

“This demolition is devastating,” tribe chairman David Archambault told NBC. “These grounds are the resting places of our ancestors. The ancient cairns and stone prayer rings there cannot be replaced.

“In one day, our sacred land has been turned into hollow ground.”

Since April, more than 3,000 Native American people have camped at the construction site in protest.

Last week, environmental groups petitioned President Barack Obama to deny permits to the construction pipe, and to revoke the standing permit from the Army Corps of Engineers. They said the pipeline could prove to be an “existential threat to the tribe’s culture and way of life”.

Vermont Sen Bernie Sanders came out in support of the protests on Thursday.

“Regardless of the court’s decision, the Dakota Access pipeline must be stopped,” he said. “As a nation, our job is to break our addiction to fossil fuels, not increase our dependence on oil.