Japan said Wednesday it will run "stress tests" on all its nuclear reactors in the wake of the Fukushima Daiichi atomic accident sparked by the March 11 earthquake and tsunami disaster.

The ongoing crisis, the world's worst atomic accident since Chernobyl 25 years ago, has ignited debate in Japan about the safety of nuclear power, which before the disaster accounted for a third of its electricity needs.

The centre-left government ordered a round of initial tests on the quake-prone country's other atomic plants after the disaster, and said the new stress tests aimed to reassure the public that the facilities are safe.

"The safety of nuclear power plants has been secured, but this is to gain a further sense of security among the people," said Trade, Economy and Industry Minister Banri Kaieda, according to the Jiji Press news agency.

Speaking on television, he added: "We are planning the stress tests to gain the understanding of local residents. We will get further confidence from the people and will restart operations at some plants."

He did not give details of what the tests would entail or when they would start, saying only they would commence soon.

An official at his ministry told AFP that the tests would be modelled on those announced recently by the European Union.

Following the Fukushima crisis, the EU ordered tests for its 143 nuclear plants, saying it would look at how they could withstand extreme and multiple disasters previously considered unthinkable.

The EU said the facilities would be checked for their ability to cope with natural disasters such as quakes and floods as well as man-made actions such as plane crashes and terrorist attacks, and combinations of such events.

Japan's nuclear crisis was sparked by a powerful 9.0 seabed quake, the country's biggest on record, that sent a massive tsunami barreling into the northern Pacific coastline, shattering entire towns.

During a power blackout, the wave knocked out Fukushima's back-up generators, which disabled reactor cooling systems and led to meltdowns, explosions and continuing leakage of radiation into the air, soil and sea.

Utilities not directly affected by the seismic disaster have refrained from restarting reactors that were under maintenance at the time, amid objections from local governments and a wave of anti-nuclear public sentiment.

Only 19 of Japan's 54 reactors are now operating, with more due to shut down for regular checks soon, forcing companies and households to save power in the sweltering summer months.

Prime Minister Naoto Kan in May told the operator of another quake and tsunami-prone plant, the ageing Hamaoka facility southwest of Tokyo, to shut down its reactors until it builds higher sea defences.

The prefectural assembly in Fukui, which hosts 13 reactors, on Wednesday said it would oppose the resumption of operations for now at five reactors that have been suspended for regular checks.

And the governor of Saga prefecture, Yasushi Furukawa, said after Kaieda's announcement that the region would await the outcome of the stress tests before deciding whether to restart two reactors at its Genkai plant.

The European Union in May announced stress tests starting June 1, saying that Japan's cascading series of disasters had shown that "the unthinkable can happen".