The country is now facing the prospect of a nuclear meltdown following a massive earthquake and tsunami.

The Telegraph reported that an International Atomic Energy Agency (IAEA) official had pointed out in December 2008 that safety rules were out of date and strong
earthquakes would pose a "serious problem" for nuclear stations.

The Japanese government had then vowed that it would upgrade safety at all its nuclear plants and it built an emergency response centre at the now stricken Fukushima plant that was designed to withstand magnitude 7 temblor. The earthquake that rocked Japan Friday measured 9 on the Richter scale.

A US embassy cable cited by The Daily Telegraph said: "He (an IAEA official) explained that safety guides for seismic safety have only been revised three times in the last 35 years and that the IAEA is now re-examining them.

"Also, the presenter noted recent earthquakes in some cases have exceeded the design basis for some nuclear plants, and that this is a serious problem that is now driving seismic safety work."

The media report said safety warnings about nuclear power plants in Japan, which is one of the most seismologically active countries in the world, were raised during the 2008 meeting of the G8's Nuclear Safety and Security Group in Tokyo.

The cables show how Tokyo opposed a court order to shut down another nuclear power plant in western Japan due to concerns about whether it could withstand powerful earthquakes.

The court ruling said there was a possibility people might get exposed to radiation if there was an accident at the plant that built to withstand a 6.5 magnitude earthquake.  A March 2006 cable said that the court's concerns were not shared by the country's nuclear safety agency.

It said: "Japan's Nuclear and Industrial Safety Agency believes the reactor is safe and that all safety analyses were appropriately conducted."  The government overturned the ruling in 2009.

There have been explosions at three of the reactors in the Fukushima plant while a fire broke out at a fourth reactor.  Prime Minister Naoto Kan appealed for calm as he asked people living in the radius of up to 20 km to leave.

Japan's chief cabinet secretary Yukio Edano said radioactivity around the damaged nuclear reactors, located 250 km north of Tokyo, had reached dangerous levels.

"We are talking now about radiation levels that can endanger human health," he said. The prospect of a nuclear meltdown at the Fukushima plant triggered panic, with many Tokyo residents deciding to leave the city.