Tokyo Electric Power Co asked a government-backed bailout body for an additional 690 billion yen ($8.7 billion) to help compensate victims of the nuclear crisis at its Fukushima Daiichi power plant.

To help Japan's biggest utility, known as TEPCO, meet costs running into trillions of yen for compensation and clean-up, the government had agreed last month to provide 890 billion yen through a bailout fund.

"We have reviewed the estimated sum of compensation after the committee addressing compensation disputes decided on additional measures to compensate victims who voluntarily evacuated," Tepco said in a statement.

The company was told by an advisory panel in October that it can expect to face bills for about 4.5 trillion yen in compensation in the first two years after the crisis, triggered by the March 11 earthquake and tsunami.

Earlier this month a separate panel on compensation guidelines said Tepco could expect bills for an additional 200 billion yen, media reported.

Trade minister Yukio Edano, who oversees energy policy, is likely to approve the latest request as early as next month, a source close to the matter said.

The March disaster knocked out reactor cooling systems at the plant, 240 kilometres north-east of Tokyo, triggering meltdowns and radiation leaks that forced some 80,000 people to leave their homes.

On Monday a report found a lack of preparation and poor communication at top levels were among the failures that turned the nuclear accident at Fukushima into the worst atomic crisis in 25 years.

A panel probing the disaster said TEPCO, as well as regulators, failed to sufficiently anticipate a massive tsunami and the devastating impact likely to result.

"The government's nuclear regulatory body did not require TEPCO to take specific measures, such as additional construction, after they received simulation results from TEPCO in 2008 and early in 2011 regarding the impact of tsunamis on their facilities," the panel said in the interim report.

In 2008 TEPCO simulated a tsunami exceeding 15 metres reaching Daiichi but did not take action, dismissing the likelihood of such a wave, the panel added.

The report also noted TEPCO did not have enough expertise on the ground after the disaster struck, saying it made mistakes like misunderstanding the functioning status of the No.1 reactor's cooling system and mishandling the No. 3 reactor's cooling system.

Reuters