All 955 gold miners trapped underground for more than a day in South Africa after a power cut were rescued unharmed on Friday, to the relief of waiting relatives.

"Everybody's out," mine spokesman James Wellsted told AFP, adding that there were no deaths or serious injuries reported.

There were "cases of dehydration and high blood pressure but nothing serious", he said.

The miners were stuck in the Beatrix gold mine, in the small town of Theunissen near the city of Welkom, for around 30 hours after a massive power outage caused by a storm prevented lifts from bringing workers on the night shift to the surface.

After several hours engineers were able to restore power, allowing the hoist to bring up the miners -- who had been trapped since Wednesday evening -- in batches.

The workers were all brought to the surface within two hours early on Friday.

"It was stressful, there was not enough ventilation," mineworker Mike Khonto told AFP. "Thankfully our management managed to send us food and water."

Wellsted said there was "no indication so far that anyone has been in distress", although it was a "traumatic experience".

A young woman, who spent the night anxiously waiting near the mine for news of her uncle, expressed her joy.

"We are relieved," she told AFP, without giving her name.

She had been among a group of miners' relatives who gathered along the road leading to the shaft, kept at a distance by security guards as they awaited developments.

Several ambulances arrived on-site overnight, said an AFP reporter at the scene.

Sibanye-Stillwater chief executive Neal Froneman said in a statement the operation was a "significant rescue effort".

- 'Utterly unacceptable' -

At sunrise the rescued workers, still in their workwear and helmets, underwent medical check-ups and left by bus.

Despite the rescue, the accident at Beatrix mine in Free State province, 290 kilometres (180 miles) southwest of Johannesburg, has reignited safety concerns at South African mines.

"We could have prevented it," said one mineworker who asked not to be named.

"They should have had some generators that were working. Security is the least of their worries. They only care about production," he said.

The National Union of Mineworkers (NUM) called on mineworkers to refuse to work in "dangerous conditions".

"Major multinational corporations like Sibanye-Stillwater which should be industry leaders in creating a safety culture are doing far too little to prevent accidents," it said.

A parliamentary committee on mining expressed outrage at the incident, calling for "drastic" action against the company.

It condemned as "utterly unacceptable" the lack of a working back-up plan to bring the workers to the surface.

The lawmakers on the committee called for "drastic actions to such acts of carelessness, including exploring possibilities of laying criminal charges against the management for attempted murder".

But mine spokesman Wellsted told AFP that "this was a very unusual event. The generators were affected by the storm."

- Depleting reserves -

Another union, NUMSA, demanded the mine should be closed until a full investigation is conducted.

"They should not be allowed to operate until they can guarantee the safety of workers," NUMSA said in a statement.

The company said operations at the mine would resume on Monday.

Last August five mineworkers died after sections of a gold mine collapsed outside Johannesburg.

In 2016 three workers stationed on the surface of a coal mine were buried when ground caved in. They were never found.

The country possesses rich mineral reserves and has some of the world's deepest gold mines.

Gold was for many decades the backbone of South Africa's economy, but production has declined sharply due to depletion of reserves.

Sibanye-Stillwater was created five years ago and is now South Africa's largest gold producer, after embarking on a string of acquisitions.

In May 2017 it bought America's Stillwater mining company to become Sibanye-Stillwater.

The Johannesburg Stock Exchange and NYSE-listed firm is also involved in platinum mining, and in December 2017 announced plans to buyout Lonmin, the world's third largest producer.