The number of people injured in a 7.2-magnitude earthquake in eastern Taiwan climbed past 1,000 on Thursday (Apr 4) though the death toll remained steady at nine, with dozens of workers on their way to a hotel in a national park mostly now found safe.

The earthquake, the strongest in 25 years, hit on Wednesday morning just as people were readying to go to work and school, centred on the largely rural and sparsely populated eastern county of Hualien.

Buildings also shook violently in capital Taipei, but damage and disruption there was minimal.

Taiwan's fire department said the number of injured had reached 1,058, putting the total number of missing at 52. Around two dozen of almost 50 hotel workers on their way to a resort in Taroko National Park had been located.

The fire department said the group was trapped on the cross-island highway, which traverses the gorge connecting Hualien with Taiwan's west coast and is a popular tourist destination.

It showed drone footage of some of the hotel workers, along with other people, waving from the side of a road, with the crushed back part of a minibus also clearly visible. Another group of 26 workers had also been found, it added.

On Thursday morning, a helicopter rescued six trapped miners. Dramatic video released by the island's Central Emergency Operation Centre showed the helicopter flying two sorties to pluck the six miners trapped in a gypsum quarry in Hualien county, near the epicentre of the quake.

A further 646 people are still trapped, most of them in hotels in the park, a key tourist attraction, as the road was cut off, the fire department said.

Rescuers knew the whereabouts of dozens more people trapped in a network of strongly built tunnels in the county, a feature of the roads that cut through the scenic mountains and cliffs leading to Hualien City from the north and west.

"I also hope that we can use today's time to find all people who are stranded and unaccounted for and help them settle down," Premier Chen Chien-jen said after a briefing at an emergency operation centre in Hualien.

The railway line to Hualien also re-opened ahead of schedule on Thursday, although one rural station north of Hualien city remains closed due to damage, the railway administration said.

In Hualien city, where people who had been trapped in buildings have all been rescued, some people slept outdoors overnight as more than 300 aftershocks rocked the region, unnerving residents

A lady, 52, who gave her family name as Yu, said she checked herself into a tent on a sports ground being used for temporary shelter late on Wednesday night because she was too scared to sleep in her apartment, which she described as "a mess".

"The aftershocks were terrifying. It's nonstop. I do not dare to sleep in the house," she said.

Dozens of residents queued outside one badly damaged 10-storey building in the city, waiting to get in and retrieve belongings.

Clad in helmets and accompanied by government personnel, each was given 10 minutes to collect valuables in huge garbage bags, though some saved time by throwing belongings out of windows into the street below.

"This building is no longer liveable," said Tian Liang-si, who lived on the fifth floor, as she scrambled to gather her laptop, family photographs and other crucial items.

She recalled the moment the quake struck, with the building lurching and furniture sliding, as she rushed to save the four puppies she keeps as pets.

"I'm a Hualien native," she told Reuters. "I'm not supposed to fear earthquakes. But this is an earthquake that frightened us."

The government also warned people to be wary of landslides or rockfalls if they ventured to the countryside for Qingming, a two-day public holiday that began on Thursday.

Families traditionally visit the tombs of their ancestors on the holiday to clean the gravesites and burn offerings.

"Do not go to the mountains unless necessary," warned President Tsai Ing-wen in a late-night message.

The official central news agency said the quake was the biggest since one of 7.6-magnitude in 1999 that killed about 2,400 people and damaged or destroyed 50,000 buildings.

Taiwan weather officials said the intensity of Wednesday's earthquake in Hualien stood at the second-highest level of "Upper 6" on a scale ranging from 1 to 7.

Such quakes collapse walls unless they are made of reinforced concrete blocks, while people cannot stand upright and must crawl to move, Japan's weather agency has said.

China, which claims self-ruled Taiwan as part of its territory, said it was "paying close attention" to the quake and "willing to provide disaster relief assistance", state news agency Xinhua said on Wednesday.

In Washington, the White House said the United States was prepared to provide "any necessary assistance".