An enormous sinkhole has appeared after an earth tremor in north-eastern Montenegro.

The 100-foot-deep hole in the snowy ground appeared near a water reservoir outside the town of Rozaje. It opened up moments after a slight earth tremor. Stunned residents insisted they had never seen anything like it before.

Ibrahim Halilovic, who lives nearby, told local media: "Nothing has ever happened like this in these parts in all the 91 years I have been around.

"I used to know the forest areas well because I was a shepherd."

The sinkhole appeared after an earth tremor
The sinkhole appeared after an earth tremor in north-eastern Montenegro
Local authorities said they did not know the cause of the sinkhole but suspect it could be due to a tunnel being built below the area.

A fence has been erected around the sinkhole as a safety measure.

The sinkhole has a diameter of 10 metres (33 feet) and is 30 metres (100 feet) deep.

Sinkholes are holes in the ground caused by some form of collapse of the surface layer.

They can form suddenly or over time and they occur all over the world.

Last July, a giant sinkhole dubbed the "gate to hell" by worried locals appeared overnight in a Russian village.

The crater was deep enough to fit a 16-storey building inside.

Speaking at the time, a local said: "It was pure luck that no-one got injured. We didn't hear anything when it happened.

"But we got really scared as the hole is really huge, and to think that something like this might suddenly appear anywhere is frightening.

"The whole Nizhny Novgorod region got shaken by this sinkhole."