A rock climber who was forced to dodge stones larger than a human hand that were allegedly thrown from the top of Kangaroo Point Cliffs says the incident could have killed him and his climbing mate.

Key points: Police believe the rocks were thrown deliberately and have been speaking to a teenager about the incident

Police believe the rocks were thrown deliberately and have been speaking to a teenager about the incident Rock climber Nick Bartlett says anyone hit by one of the rocks could have been killed

Rock climber Nick Bartlett says anyone hit by one of the rocks could have been killed The Australian Climbing Association says such incidents are rare

Climbers called police on Monday night to report someone tossing stones at them as they scaled the cliff face.

Police arrived at the scene a short time later and have been questioning a teenager over the matter.

Rock climber Nick Bartlett said he was on the ground when there was a "great big thump" beside him.

He said at first he and other climbers thought it was a natural rockfall.

However, by the time 10 stones had fallen nearby, all of different sizes, they suspected someone was throwing them down.

"We didn't know if they were really trying to hurt someone, or some silly kids," he said.

Those at the bottom pressed themselves tightly against the cliff face in the hope of finding some protection from the falling rocks.

'It could have led to two deaths'

David Reeve from the Australian Climbing Association of Queensland said such incidents were dangerous, but rare.

Mr Bartlett said while climbers expected the occasional rock to fall towards them while climbing, this was a "scary one-off".

He said the level of danger was clear to his climbing partner, who was exposed on the cliff's face and a possible target.

Mr Bartlett indicating one of several rocks that fell as he and a friend were climbing at Kangaroo Point. ( Supplied: Nick Bartlett )

"If they were to drop a rock above him, there's nothing to stop him from being dead at that point. He's completely exposed," Mr Bartlett said.

"So he's being very, very quiet and really hoping they don't decide to start throwing rocks where he is."

He said there was no way the person throwing rocks could see climbers near the bottom, making their actions "pretty bloody reckless".

Mr Bartlett said he was belaying at the cliff base at the time — anchoring the rope that ensured his partner stayed safely in place.

"Say the rock had hit me, it could have led to two deaths," he said.

"I'm in control of how the rope moves so if it hits me and I let go, the rope slides through the control device.

"He would fall to his death probably."