Nobody likes having to stand around and wait for their bus to turn up, but believe us when we tell you – things could be a whole lot worse.

This stunning footage emerged online last week, showing five people in the Chinese city of Harbin being swallowed without warning by a sinkhole that emerged underneath their feet while they were waiting at a bus stop.

Local authorities said four people received minor injuries in the accident, but luckily nobody was killed. Harbin is the provincial capital of Heilongjiang, in the country's northeast.

The freak incident, captured by a nearby surveillance camera, shows just how suddenly sinkholes can strike. If you pay attention to the footage, you can see how none of the pedestrians involved stood even a slim chance of escaping when the ground gave way.

One second they're just standing there, oblivious to the geological event about to engulf them, the next, they're in free-fall, along with the ground they were standing on and a large sign that forms a rough landing platform for one of the victims. Of the five caught by the sinkhole, one lady manages to cling to an underground pipe to prevent herself falling further into the 3-metre-deep void.

In a longer clip of the same scene (embedded below), you can what occurred directly before and after the ground gave way. Pedestrians pass along the footpath in both directions, unwittingly clearing the sinkhole zone with just seconds to spare before it opens up behind them. Those stationary at the bus stop aren't so lucky.

After the ground subsides, onlookers cautiously approach the edge of the sinkhole, and the lady clinging to the pipe is assisted up.

At this point it's unknown what caused the footpath to collapse. While sinkholes can result from human activity, such as mining and tunnelling, they're also a natural occurrence. Natural sinkholes are often caused by the process of erosion, where water becomes acidic from exposure to carbon dioxide and dissolves rock layers underneath the surface.

"Once those caves start to collapse, the materials above will simply funnel in," Anthony Cooper, a geologist with the British Geological Survey, told Jon Henley at The Guardian.

Sinkholes are a common problem in China, often due to human causes. It's estimated that one particularly badly affected city, Jining, will require some 5 million of its inhabitants to relocate this century as a result of major sinkhole activity stemming from extensive mining in the region.