Japan Rocked by Fresh Blast at Fukushima Nuclear Plant

The nuclear crisis in Japan escalated as a third explosion in four days rocked the struggling power plant in the country's stricken north-east, according to its nuclear safety watchdog. Tokyo had already called in international help to tackle the escalating crisis.

Non-essential personnel pulled back from reactor 2 at the Fukushima No 1 power plant as radiation levels rose following the blast at 6.10am Japanese time. The blast appears to be the most serious yet, with Kyodo news agency reporting possible damage to the suppression pool of the containment vessel - increasing the risk of a significant release of radioactive material. The news agency said the safety agency feared radiation was leaking.

It came as the official death toll from the worst earthquake and tsunami in Japan's recorded history reached almost 1,900, with tens of thousands still unaccounted for. Millions of survivors woke up to a fifth day in the disaster zone with dwindling supplies of food and fuel, following another 24 hours of aftershocks, blazes and tsunami alerts.

Officials had previously admitted the reactor could be in partial meltdown and warned the situation was "even worse" than in the other two units with cooling problems. "Although we cannot directly check it, it's highly likely [to be] happening," Yukio Edano, the chief government spokesman, told reporters. A second dramatic hydrogen explosion had blown the walls off another reactor unit yesterday.

As Tokyo struggled to handle the spiralling crisis, it asked the United Nations nuclear watchdog for expert help and the US nuclear regulatory commission for equipment. Officials also began to distribute potassium iodide, which can help inhibit the uptake of radioactive iodide by the thyroid, to evacuation centres. They have already evacuated hundreds of thousands of residents within a 12-mile radius of the facility.

Yukiya Amano, director general of the International Atomic Energy Agency, stressed it was "unlikely that the accident would develop" like Chernobyl, and said the reactor vessels remained intact. Officials in Japan had earlier suggested one might have been breached.

Several countries said they would screen Japanese produce for radiation as a precaution. US officials said military personnel taking part in rescue efforts registered low levels of radioactive contamination after flying by helicopter back to their ships off the Japanese coast. They were cleared after a scrub-down, but the ships moved position as a precaution.

The desperate shortage of supplies was a more immediate concern for the millions facing a fourth night in near-freezing temperatures. The Japanese broadcaster NHK reported that many emergency shelters were running out of food and fuel, leaving weakened survivors cold and hungry.

"People are surviving on little food and water. Things are simply not coming," Hajime Sato, a government official in Iwate, told Associated Press. He said the prefecture was receiving just a tenth of the food and supplies it needed. "We just did not expect such a thing to happen. It's just overwhelming," he said.

With aftershocks of up to magnitude 6.1 continuing, survivors fled to high ground on Monday morning as sirens blared and broadcasters announced a tsunami alert. It later proved to be a false alarm.

But Friday's 9-magnitude quake and tsunami have already left around 1,000 bodies on the shores of the Oshika peninsula and a further 1,000 bodies in Minamisanriku, according to officials and police in Miyagi province. Around 9,500 people remain uncontactable in the latter town. The Kyodo news agency said police and firefighters were still trying to recover 200 to 300 bodies in Sendai.

Japan's central bank injected 15 trillion yen (PS113bn) into money markets to stabilise the country's economy in the wake of the disaster. But the benchmark Nikkei 225 stock average slid 6.2%.

AP reported that the outspoken governor of Tokyo, Shintaro Ishihara, had described the disaster as a "punishment from heaven" because the Japanese had become greedy.