A reporter was struck in the back by a rubber bullet fired by US police during a peaceful demonstration against a controversial pipeline project.

Video footage shows journalist Erin Schrode writhing in agony after the projectile strikes her in the lower back while she is interviewing a protestor at Standing Rock in North Dakota.

Schrode was covering a demonstration by thousands of people against the $3.7 billion Dakota Access oil pipeline. Opponents say it cuts across sacred Native American burial grounds and threatens to pollute local rivers.

The video begins showing protestors, or “water protectors” as they are known, by a river facing police clad in riot gear on the opposite bank.

Schrode is interviewing a man when she suddenly screams “Ow” and falls to the ground as the rubber bullet strikes her.

In a Facebook post, she says she was badly shaken after “militarized police” shot her at “point-blank range”.

Speaking after the event she recalled being unaware what had happened but just felt “excruciating pain”.