BISMARCK, N.D. -

A South Dakota tribal chairman has urged members to avoid Bismarck and Mandan in North Dakota after a clash between private security guards and people protesting against the Dakota Access Pipeline.

Cheyenne River Sioux Tribal Chairman Harold Frazier said in a statement Sunday his members were among protesters pepper-sprayed by security officers and attacked by dogs at the pipeline construction site Saturday on private land north of the Standing Rock Sioux Reservation in North Dakota, south of Bismarck.

Hundreds of people from across the country have joined the Standing Rock Sioux to protest the pipeline.

Tribal leaders say construction crews have destroyed American Indian burial and cultural sites.

North Dakota Gov. Jack Dalrymple's office Sunday urged protesters "to participate only in peaceful and lawful activities."