Image copyright Lochaber MRT Image caption The walkers were found to have had no winter kit

Rescuers said four people helped from Ben Nevis were lucky to be alive.

They said the tourists who were caught in blizzard conditions had "no ice axes, no crampons and as far as we are aware, no maps". Three of them were wearing trainers.

Lochaber Mountain Rescue Team found them near the summit of the mountain.

All four were taken by helicopter from part-way down the mountain to be checked over at Belford Hospital in Fort William.

Inverness Coastguard helicopter, Rescue 151, could not be used near the summit because of the severity of the conditions.

'Very, very cold'

Miller Harris, of Lochaber MRT, said the four people who were visiting Scotland from abroad were lucky to have been at a place on the mountain where they could get mobile phone reception.

They were able to raise the alarm by calling the police and then use an app to give rescuers a location "within metres" of where they were.

Mr Harris told BBC Scotland: "If there hadn't been a phone signal, we would have had no idea what was going on.

"One of them managed to get back to the summit where they met our team and was able to confirm the location where his friends were.

"They were very, very cold and one was probably hypothermic and was having difficulty walking."

Mr Harris said the people were on a day trip, rather than being experienced hillwalkers, and had no winter equipment such as ice axes or crampons and did not appear to have a map.

Image copyright Lochaber MRT Image caption Inverness Coastguard helicopter assisted in the rescue

Lochaber MRT described the weather as "horrendous" with the wind chill of -20C or below.

The rescue on Britain's highest mountain came in the wake of Storm Ciara and amid Met Office yellow "be aware" warnings of high winds and snow.

The group used the app What3words to give a location "within metres" of where rescuers found them.

The app divides the world into three-metre squares and gives each one a unique three-word address.

Tortoises, swarm and announce were the words given for the group of four on Ben Nevis, according to the What3words website.

In Scotland, it has previously been used in the rescue of an injured walker in Lewis in the Western Isles .

Mountaineering groups suggest the app be used in addition to but not instead of map and compass and other winter skills.

Mr Harris backed that advice, adding: "We are not saying that people should not go out on the mountains. People with the right skills and equipment are able to do that safely."