Japan | Fukushima plant radiation is leaking 'directly' into atmosphere

Radiation from Japan's quake-stricken Fukushima Daiichi nuclear plant on the Eastern coast has reached harmful levels, the Japanese government says. The warning comes after the plant was rocked by a third blast which appears to have damaged one of the reactors' containment vessels for the first time. If it is breached, there are fears of more serious radioactive leaks. The danger zone has been extended, warning residents within 30km to evacuate or stay indoors. 

Japan had officially asked the UN atomic watchdog to send a team of experts to help in the current nuclear crisis, International Atomic Energy Agency (IAEA) chief Yukiya Amano has said.

Earlier, reports suggested that nuclear fuel rods at the quake-stricken nuclear reactor at Fukushima are now fully exposed, Jiji news agency said, quoting the plant's operator, Tokyo Electric Power Co.

The report referred to the Fukushima Daiichi complex's No.2 reactor, where levels of water coolant around the reactor core had been reported as falling earlier in the day.

The Jiji report said a meltdown of the fuel rods could not be ruled out. A meltdown raises the risk of damage to the reactor vessel and a possible radioactive leak, experts say.

Plumes of grey smoke rose from the number 3 unit after the blast ripped through the facility.

The reactor had been under emergency watch for a possible explosion as pressure built up there following a hydrogen blast on Saturday in the facility's number 1 unit. 

Japan's chief cabinet secretary Yukio Edano said the reactor's inner containment vessel holding nuclear rods is safe, allaying some fears of the risk to the environment and public.

He said that the possibility of a radioactive leak was "low".

But he added that people within a 20km (12 mile) radius were being ordered to stay inside.

Tokyo Electric Power Company says seven people are missing and three are injured after the blast at the plant which is 150 miles (241km) north of Tokyo.

Officials have been racing to stave off multiple reactor meltdowns after a devastating quake and tsunami incapacitated the Fukushima plant.

They had to resort to cooling the reactors down with sea water.

More than 180,000 people have evacuated the area, and up to 160 may have been exposed to radiation.

Prime Minister Naoto Kan said the situation at the Fukushima nuclear plant remained "worrisome" and that the authorities were doing their utmost to stop damage from spreading.

On Sunday he said the disaster was the biggest crisis the country had faced since World War Two.

The nuclear crisis was triggered by twin disasters on Friday, when the 9.0 magnitude earthquake was followed by a tsunami that ravaged Japan's north-eastern coast.

More than 1,400 people were killed, but a police chief said the death toll may be over 10,000.

The International Atomic Energy Agency (IAEA) has also declared a state of emergency at the Onagawa site after excessive radiation levels were recorded there.

And the cooling system pump has failed at the Tokai facility but the back-up is working, according to an official.

The Japanese government is planning rolling blackouts and a limited number of trains will be running in Tokyo so energy supplies can be saved.

Elsewhere, a wave of around 3m (10ft) was reported off the coast of northeast Japan by a helicopter, leading to warnings of another tsunami.

Residents were ordered to flee to higher ground by Japanese soldiers after reports of a sea level change.

However, the Japanese Meteorological Agency said no tsunami had been spotted and it proved to be a false alarm.

Earlier a strong offshore tremor struck 150km (90 miles) northeast of Tokyo shaking tall buildings in Japan's capital, but authorities did not issue a tsunami alert.

The country has suffered over 150 aftershocks since the "megaquake" hit on Friday.

There is currently a warning that there is a 70% chance of another strong quake of 7.0 magnitude or over occurring.