The operator of Japan's crippled Fukushima nuclear power plant said Wednesday it will abandon seven underground reservoirs storing radioactive water after three of them sprang leaks.

The contaminated water will be transferred to more reliable containers on the ground, possibly by early June, to avoid risks of further leaks, Tokyo Electric Power Co. (TEPCO) president Naomi Hirose told a news conference.

"We have yet to grasp the cause of the leaks. But we will strengthen monitoring activities so as to prevent the water from flowing into the sea," he said. "We want to transfer the contaminated water from the underground reservoirs as soon as possible."

Three of the underground reservoirs were found to have leaked contaminated water since April 5 at the Fukushima Daiichi plant which was crippled by the March 2011 earthquake and tsunami.

The enclosed reservoirs store water that has been used to cool down the reactors after caesium is removed but while other radioactive substances remain.

TEPCO said it will transfer about 7,000 tonnes of contaminated water from two of the three leaking reservoirs to tanks on the ground.

It will also build 38 new tanks on the ground with total capacity of 19,000 tonnes by mid-May.

Failures at the plant, more than two years after it was hit by the disaster that caused meltdowns and sent tens of thousands fleeing from their homes, have underlined the precarious state of the facility.

Meanwhile, Japan's nuclear watchdog on Wednesday published new draft safety standards that it hopes will prevent a repeat of Fukushima, the worst nuclear accident since the 1986 Chernobyl disaster.

The Nuclear Regulation Authority (NRA) said measures must be taken to defend atomic power plants against tsunamis, earthquakes and terrorist attacks.

Under the proposed rules there will be a ban on building reactors near active tectonic faults, which themselves will be redefined in a move that will make many more of them fit that definition.

At present, active faults are defined as those that have moved in the last 130,000 years, but the NRA will move the benchmark to any time in the last 400,000 years.

Up to five nuclear plants in Japan sit atop a possible active seismic fault, NRA-appointed experts have said.

NRA chairman Shunichi Tanaka said earlier this year that plants would have to be able to survive a direct hit from a hijacked airliner or ship, as well as withstand tsunamis like the one that crippled Fukushima.

The move comes after repeated criticism that lax regulation and an overly cosy relationship between authorities and the big-money companies they were supposed to police worsened the Fukushima plant catastrophe.

Hundreds of thousands of people were made homeless by the disaster and tracts of prime agricultural land were left unfarmable after radiation spread across a large area.

Anti-nuclear sentiment is running high in Japan, which used to rely on atomic power for around a third of its electricity needs.

The proposals will now go out to public consultation for 30 days and new rules will come into force in mid-July.

All but two of Japan's reactors remain offline after being shuttered for regular safety checks in the aftermath of the 2011 crisis.