Seventy-four workers were killed after a gas blast early Sunday at a northern Chinese colliery, the worst accident to hit the nation's mines in over 14 months.

More than 400 miners were on the job when the pre-dawn explosion ripped through the mine, the official Xinhua news agency reported. A number of victims died after being rescued, it said.

Dozens of miners were reported trapped at the site outside Taiyuan, capital of the main coal-producing province of Shanxi, with some reportedly calling their families on mobile phones from underground.

Xinhua later said rescue operations ended in the early evening with all workers retrieved.

"The focus of our effort has shifted from searching and rescue to medical treatment," provincial Communist Party committee chief Zhang Baoshun, who was leading the rescue effort, was quoted as saying.

The death toll makes this the most lethal accident reported in China's disaster-prone mining industry since 105 people died in a mine explosion in December 2007, also in Shanxi province.

China's President Hu Jintao and Premier Wen Jiabao had issued instructions to do everything possible to save those still trapped inside the mine, state television reported.

Vice Premier Zhang Dejiang was dispatched to the scene to oversee rescue efforts, Xinhua reported. He said a team would be set up to investigate the incident.

One of the survivors, 27-year-old Xue Huancheng, said he and his co-workers initially were not aware how serious the accident was and were not ordered to leave the mine until more than an hour after the blast.

"At that time the power supply underground was cut off and we had to walk," he told Xinhua from his hospital bed. He added he reached the mouth of the mine after 50 minutes, at which time he fainted from lack of oxygen.

Xinhua said dozens of rescuers had gone underground at midday in search of those still missing. A total of 436 were at work when the blast erupted, and more than 300 miners escaped alive, the agency reported.

One man told Xinhua that a mere coincidence had saved him from being among those trapped at the Tunlan coal mine.

"I should have been among them, had I not changed my shift with another miner," said the man, who declined to be named. "He is still underground. I hope he is alive."

According to state media, about 3,200 people died in Chinese coal mines in 2008.

However, independent labour groups have long maintained that China's mining death toll is much higher than the government says, as local mine bosses and regional leaders cover up accidents to avoid fines and costly mine shutdowns.

Government figures also show that almost 80 percent of the nation's 16,000 mines are illegal.

Most of the miners rushed to hospital after Sunday's accident had suffered carbon monoxide poisoning, Xinhua said, citing doctors at the Xishan Hospital of Coal and Electricity.

A photo posted on the Internet showed one of the survivors, apparently unconscious and with a blackened face, being rushed to medical treatment.

A total of 114 miners were under observation at hospital, with five in serious condition, according to Xinhua.

The mine, which has an annual capacity of five million tonnes, is operated by the Shanxi Jiaomei Group, according to Xinhua.

It said that it was considered a relatively safe mine, with no accidents reported over the past decade.

Zhang Baoshun, the head of the Communist party in Shanxi, told miners to take care and avoid getting hurt while carrying out their dangerous work.

China has vowed for years to improve safety at its mines, but has been hampered by a lack of resources to effectively supervise the sprawling industry, a major employer of destitute migrant workers.