About 100 masked attackers destroyed a security checkpoint in China’s northern region of Inner Mongolia, injuring 13 people and wrecking 11 vehicles, state media said late on Sunday.

The large mob pepper-sprayed staff, tied them up and threatened to beat them to death, the China News Service said.

The report did not provide a motive for the Sunday attack on the security post in Ejin county and Reuters was unable to reach officials for comment.