Japan's crippled Fukushima nuclear plant has sprung yet another leak of radioactive water, its operator said on Thursday, the latest in an increasingly long line of mishaps to rattle public confidence.

Tokyo Electric Power Co (TEPCO) said around 22 litres (six US gallons) of highly radioactive waste water leaked from a pipe as work crews were trying to empty a reservoir that itself had already sprung leaks.

The company said it has not seen any evidence that the leaked water had gone beyond the confines of the plant.

"We are starting to dispose of the soil... that is believed to have been affected with the leaked water," TEPCO said in a statement.

The new problem came only a day after TEPCO announced a plan to empty seven underground reservoirs storing radioactive water after three of them sprang leaks.

Two years since the worst nuclear accident in a generation erupted, the plant remains fragile, with systems to cool spent nuclear fuel failing repeatedly in a matter of weeks in March and April.

The plant was hit by a 9.0-magnitude earthquake and massive tsunami on March 11, 2011, prompting reactor meltdowns that forced tens of thousands of people to flee their homes.

Many remain displaced and some will never be able to return.

A team of specialists from the International Atomic Energy will inspect the plant next week at the request of the Japanese government.