A mountain biker fears someone could have been seriously injured after booby traps were found along a popular trail.

Nic Sullivan was riding with a mate at Bethune Gully on Saturday afternoon, when he landed on a big log near a landing spot.

He was able to land quickly and lift his front wheel over the log, but said if he had been going a bit faster "it could have been much worse".

NIC SULLIVAN/SUPPLIED Logs block a mountain bike trail at Bethunes Gully, Dunedin.

"Initially I thought it had either fallen or rolled onto the track, until I looked at the last few jumps and saw another big log had been placed in the middle of its take off."

After moving the two logs off the track, they came across more traps, including three sticks wedged at chest or head height between two trees near a blind corner.

After clearing the track, they again went on another run but founds more logs where they had been 20 minutes before.

NIC SULLIVAN/SUPPLIED Traps block a mountain biking trail at Bethunes Gully, Dunedin.

Only one group walking a dog had been spotted during their run.

They found more logs laid near corners on their next run, as well as another stick placed at head height.

"What was worse was the very large log that had been placed lengthways under the drop, which had a number of broken off branches that could easily have impaled anyone who would be unlucky enough to fall on it," Sullivan said.

He had alerted other mountain bike users about the traps, and believed they had been placed to hurt or intimidate riders.

Dunedin City Council Recreation Planning and Facilities Manager Jendi Paterson said "We're really concerned - obstacles like this on the track are very dangerous".

"Our contractor will be removing the logs and branches."

People were encouraged to contact council if they saw "anything on our tracks that creates a risk for track users so we can react as a matter of priority".