Japan has gone into a state of maximum alert after plutonium was found in the soil around the damaged Fukushima nuclear plant and radioactive water leaked from a reactor in the plant.

Prime Minister Naoto Kan said on Tuesday the crisis scenario continues to be unpredictable around Fukushima and that the country was now in a state of maximum alert.

Talking to Parliament, the prime minister also said the government will consider the extension of evacuation zone around the plant. Echoing Kan's concerns, the chief cabinet secretary too said the Fukushima crisis was very grave now.

We need to avoid the fuel rods from heating up and drying up. Continuing the cooling is unavoidable... We need to prioritize injecting water, he said.

Meanwhile, more countries are reporting traces of radiation in water, food and air after the Fukushima nuclear reactors started releasing radioactive elements following the quake and tsunami earlier in the month. Reports from Vietnam, South Korea, the United States and China say radioactive elements have reached their shores from Japan.