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BISMARCK, N.D. (AP) _ A South Dakota tribal chairman is urging members to avoid Bismarck and Mandan in North Dakota after a clash between private security guards and people protesting the Dakota Access Pipeline, saying he fears for his people’s safety.

Cheyenne River Sioux Tribal Chairman Harold Frazier said 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. He urged tribal members to avoid traveling to or doing business in the area.

Hundreds of people have joined the Standing Rock Sioux to protest the pipeline. Tribal leaders say crews have destroyed American Indian burial and cultural sites.

The Bismarck Tribune reports North Dakota Gov. Jack Dalrymple’s office Sunday urged protesters “to participate only in peaceful and lawful activities.”