Japanese traditional performers wearing devil masks dance for the "Hanami" or flower viewing, at a temple in the tsunami devastated area in Rikuzentaka city, Iwate prefecture on Sunday.

The operator of Japan's tsunami-hit nuclear plant said Sunday it aims to reduce radiation leaks within three months and to achieve a "cold shutdown" within six to nine months.

Japan's embattled Tokyo Electric Power Company (TEPCO) offered the timeline more than five weeks after a giant quake and tsunami knocked out at its six-reactor Fukushima Daiichi station.

The damage sent atomic core temperatures soaring in partial fuel rod meltdowns, in what became the world's worst nuclear crisis in 25 years. It has also left the country facing crippling power shortages.

Radiation has leaked into the air, soil and sea from the coastal plant northeast of Tokyo, as emergency crews have doused overheating reactors and fuel rod pools to prevent full meltdowns of volatile .

TEPCO's chairman Tsunehisa Katsumata said at a press conference that the utility aims to cool reactors and start substantially reducing radiation from the explosion-charred facilities within three months.

Within six to nine months, TEPCO said in a statement, it expects to achieve "cold shutdowns" of all the six reactors, a stable condition in which temperatures drop and radiation leaks fall dramatically.

"As the short-term targets, we have set two steps," said Katsumata. "Step one is to steadily reduce the amount of radiation.

This handout picture taken by a Tokyo Electric Power Co remote controlled drone on Friday and released on Sunday shows the yellow top part of the nuclear reactor containment vessel at the fourth reactor building of TEPCO's Fukushima No.1 nuclear power plant.

"In step two, we aim to control the release of and greatly control the amount of radiation."

"There are various risks ahead," he cautioned. "But we aim to complete step one in about three months and step two in another three to six months."

TEPCO also said it would put special covers on the heavily damaged one, three and four outer buildings.

The company said that an initial focus would be on preventing new hydrogen explosions in reactors by injecting nitrogen, and on avoiding further releases of into the environment.

Katsumata also apologised and said he was considering resigning over the crisis, which has sparked anger and criticism over the information TEPCO has provided.

Prime Minister Naoto Kan called the plan "a small step forward", Kyodo News reported.

This handout picture taken by a Tokyo Electric Power Co remote controlled drone on Friday and released on Sunday shows the wrecked south side wall of the fourth reactor building at TEPCO's Fukushima No.1 nuclear power plant.

Trade and industry minister Banri Kaieda earlier said the roadmap would help move the from the emergency phase into a stabilisation phase.

"The government urges TEPCO to carry out the roadmap steadily or carry it out faster than planned," he said.

Kaieda added that in six to nine months the government would review the evacuation area around the plant, having set a 20-kilometre (12-mile) exclusion zone and urged people to also leave from a wider 30-kilometre radius.

Japan has raised the level of the crisis from five to the maximum seven on an international scale, the same "major accident" category as the 1986 Chernobyl disaster, although it stressed that far less radiation has been released.