Japan's Trade and Industry Minister, Banri Kaieda, said the three senior officials would be held responsible for mishandling the plant and its problems.

Radioactive material is still leaking from the plant nearly five months on.

The crisis has also brought to light the close links between the government and the power industry.

Those sacked are the head of the nuclear safety agency, Nobuaki Terasaka, the head of the agency for natural resources and energy, Tetsuhiro Hosono, and the vice-minister for economy, trade and industry, Kazuo Matsunaga.

Mr Kaieda, who played a key role in handling the Fukushima crisis, has also said he plans to resign to take responsibility.

But he has not said when he will do so, despite a tearful confrontation with opposition lawmakers.

*** Also, the Japanese government and central bank have intervened to weaken the yen to protect economic growth.

Japan sold yen on the markets, weakening the currency so that the dollar was worth more than 79 yen, up from about 77 yen before the move.

The Bank of Japan (BOJ) announced further monetary easing in the afternoon.

These were unilateral moves by Japan, unlike an intervention in March, which was backed by the G7 group of nations.

Analysts questioned whether the intervention would have any long-term impact.

The BOJ said it would make more money available to financial markets by expanding a programme to buy government bonds and other securities.

The central bank will increase the money associated with that programme from 40 trillion yen (US$504 billion) to 50 trillion yen.

It said it would achieve this by the end of 2012.