Thousands told to stay inside as plant leaks radiation

Frightening new warnings were issued in Japan yesterday imploring people near the Fukushima power plant to stay indoors and make sure their homes were airtight as experts acknowledged that radiation leaks had reached dangerous levels.

As officials conceded that the conditions around the damaged Fukushima Daiichi power plant had dramatically deteriorated following a fourth explosion, 140,000 people were ordered to protect themselves. The instruction came as the wind direction, which had previously taken any radiation out to sea, shifted towards Tokyo. It was expected to reverse again this morning.

"Please do not go outside. Please stay indoors. Please close windows and make your homes airtight. Don't turn on ventilators. Please hang your laundry indoors," said the Chief Cabinet Secretary Yukio Edano, adding: "Now we are talking about levels that can damage human health. These are readings taken near the area where we believe the releases are happening. Far away, the levels should be lower."

In addition to the explosions, a second fire broke out at the plant's number four reactor last night after the intial blaze was not extinguished properly. It was also reported that water levels were falling at the number five reactor. Eight hundred non-essential staff were evacuated while 50 workers remained behind in their continued urgent efforts to try to cool the reactors. The International Atomic Energy Agency (IAEA) confirmed that readings of 400 millisieverts (mSv) per hour were registered outside the Fukushima site at one point – a dangerously high level.

In a televised statement, Prime Minister Naoto Kan urged those within 19 miles of the nuclear plant to stay indoors: "The level seems very high, and there is still a very high risk of more radiation coming out." While he called for calm, the warnings fuelled panic in Japan and around the world. With the death toll now 3,300 since the earthquake and tsunami on Friday, and tens of thousands missing, fears rose that there would be casualties among the 17,000 UK citizens known to have been in the country. "As yet there are no confirmed British fatalities, but we have severe concerns about a number of British nationals," David Cameron told MPs as the Government called on people to confirm they were safe.

A UK international search and rescue team is looking for survivors. A spokesman for the Department for International Development said the team had gone in to clear a large residential and industrial area in the centre of the disaster zone but found no one alive.

The full extent of the disaster, with whole villages and towns wiped off the map, was becoming increasingly evident as a massive international humanitarian effort continued. At least 1.5 million households were facing a fifth night of little food, running water or electricity in near-freezing weather. Almost half a million people are in temporary shelters.

Hundreds of aftershocks have shaken the north-east and Tokyo but experts said the risk of another tsunami was receding. An aftershock measuring 6.1 on the Richter scale was reported yesterday, with an epicentre around 60 miles from the Hamaoka nuclear power plant, though the IAEA said it was continuing to operate safely.

As experts at the Fukushima Daiichi plant battled to avert a disaster, radiation levels in Tokyo were reported to be slightly elevated but far too small to threaten the 39 million people in the capital.