New Zealand's largest active volcano, Mount Ruapehu in the North Island, has been showing signs of increased activity and scientists are warning it may erupt.

But up on the mountain tourism operators are not too concerned. They are more worried that the media reports have scared off visitors.

Meanwhile newspaper headlines in New Zealand are reading "Restless Ruapehu emits danger signs" and "Molten rock on the move".

Dr Tony Hurst is a volcanologist based in Wellington and has been monitoring volcanoes across New Zealand for 30 years.

He says close attention needs to be paid to Ruapehu, particularly because of the number of people who ski on its slopes. Dr Hurst says Mount Ruapehu began stirring three weeks ago.

"We've put out a release to say that there is a bit more gas detected," he said.

"The temperature of the lake is in the high 30s but it's not going down, so we wonder what's happening."

In September last year, Mount Ruapehu erupted.

An Auckland school teacher became trapped in a hut and had to have part of his leg amputated when he was hit by falling rocks.

Dr Hurst says the September eruption was an example of how suddenly the mountain can change.

"Last year we didn't have any warning, any time you can get something out of it," he said.

He says while there may not be a huge chance of an eruption, he is determined that people are always aware of the risk.

"I'd only put it at a three (out of 10 chance) but there are some times when we are really concerned about it like in 1996 and within two days we got a major eruption," he said.

"We've probably got about 50 like this and it will go off."

Volcanic shadow

Garth Steven runs the Whakapapa Holiday Park, which is the closest accommodation to the volcano.

He has lived in the shadow of the volcano for two years and says he was attracted to the place by the magic of the mountain.

"Beautiful place, one of the best places in the world, the ground is alive," he said.

He knows the scientists have a job to do, but he believes the media has exaggerated the risk and only picked up the Ruapehu warning a fortnight after it was issued.

"It did seem to be a quiet news time and it's upsetting just before the start of the ski season," he said.

He says he has had lots of phone calls from friends in Australia warning him him he is in danger.

He is not worried about his safety, his main concern is the health of his business.

"Haven't had any cancellations yet, we've had a good snowfall and good bookings and I've had a few ring and ask, but we haven't had a lot of cancellations," he said.

"I believe not many in Australia know how good the snow is in the north island, for all the thrill seekers out there come over and ski an active volcano and write home about it."