Thousands of people in Tokaimura rushed to have their radiation levels checked yesterday after the authorities finally declared that the runaway nuclear accident at a uranium-processing plant was under control.

More than 7,000 people queued at the Tokai Culture Centre, where local government officials and nuclear facility workers offered medical checks.

In Tokyo, the government admitted its response at the start of the 20-hour crisis - the length of time radiation was escaping - had been flawed.

"Our recognition of the seriousness of the incident was poor. We have to frankly admit that," said the chief cabinet secretary, Mr Hiromu Nonaka, adding quickly: "But this does not mean concerns about our country's entire nuclear programme arise."

Safety would be reviewed, said the science and technology minister, Mr Akito Arima. In Tokaimura, meanwhile, managers abased themselves, literally, to apologise for the accident.

"I think it was caused by human error on the part of plant employees," said Mr Moriki Aoyagi, president of Sumitomo Metal Mining, the parent firm of the company running the site. He apologised at a news conference, bowing deeply before an audience of reporters.

In a community hall where residents had sought shelter, Mr Koji Kitani, president of JCO Ltd, operators of the plant, knelt on the floor to offer his apologies. Popular anger was not assuaged, however.

"This is unforgivable. It is no different from them making bombs inside," said Sumiko Fuseya (63), medical director at Hitachi Tokaien, the biggest home for the elderly in the area.

"I want all their facilities to move. I want them to get everything fixed even if that means risking their own lives."

"It is very scary," said Nori Takita (74). "I had not been worried about the nuclear facility, but this incident has changed my mind."

Foreign residents in the region watched bilingual TV and scoured the Internet for information on the accident. Ms Fiona Kelly from Derry who lives in the next prefecture (county) to Tokaimura's said local TV said it was safe for people in the Tokaimura area to eat vegetables from local shops.

But apart from people seeking medical tests, the residential area around the plant remained a ghost town yesterday, despite the general all-clear from the government. All shops were closed with police officers stationed to seal off the area, wearing white raincoats with hoods to protect themselves.

The town, about 70 miles north-east of Tokyo, called on residents to be calm.

"There is no fear of a further spread of nuclear radiation," a town official announced through loudspeakers, which echoed on the streets. "Please remain at home for a while until we can complete our safety check."

Forty-nine people were exposed to large doses of radiation by the accident. They included three workers, two of whom remain in a critical condition after receiving extremely high doses of radiation.

It will be some time before the extent of contamination spreading out from the location of the accident is fully known and its implications understood. Yesterday, however, the director of the International Atomic Energy Agency division of radiation and waste safety, Mr Abel Gonzalez, played down comparisons between Tokaimura and the Chernobyl disaster of 1986.

"This is not an accident which will leave residual contamination in the outside environment," he noted, saying that in his view "this accident cannot be compared with Chernobyl."

However, the IAEA said the accident was certainly the most serious such incident since Chernobyl. It was being rated provisionally as four on the seven-level scale of nuclear incidents, on which Chernobyl rated seven.

"This is in terms of casualties, in terms of effect on human health of people in the neighbourhood, a very significant accident indeed," said an IAEA spokesman, David Kyd.

Greenpeace is to send a team of three experts to Japan to evaluate the effects of the accident. According to it, the Japanese government has yet to reveal the full truth about the gravity of the accident.

"Maybe that's because it doesn't know itself," said Diederik Samson.