Factbox: Timeline of Japan's unfolding nuclear crisis

Japan Atomic Power says the cooling process was working at its Tokai No 2 nuclear power plant's reactor although two of the three diesel power generators used for cooling were out of order.

01:43 - Japan Atomic Power says the cooling process was working at its Tokai No 2 nuclear power plant's reactor although two of the three diesel power generators used for cooling were out of order. The reactor at the plant, about 120 km (75 miles) north of Tokyo in Ibaraki prefecture, was automatically shut after Friday's massive earthquake and tsunami.

07:29 - TEPCO says it has reported a rise in radiation levels at its Fukushima Daiichi nuclear power plant to the government.

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11:11 - Domestic media image shows smoke rising from the No 3 reactor at Japan's Fukushima Daiichi nuclear plant. Japanese TV says there was a hydrogen explosion at the plant.

11:20 - Japan's nuclear safety agency confirms a new explosion rocked Japan's stricken Fukushima Daiichi nuclear power complex, sending a plume of smoke into the air. But it says it cannot confirm whether or not the hydrogen explosion at the plant's No.3 reactor has led to an uncontrolled leak of radioactivity.

11:40 - Jiji quotes TEPCO as saying a fresh explosion that rocked the Fukushima Daiichi nuclear power complex has not damaged the plant's No 3 reactor vessel.

12:43 - Chief cabinet secretary Yukio Edano says a large-scale radiation leakage is unlikely from the Fukushima Daiichi nuclear power plant's No 3 reactor hit by an explosion after cooling problems.