The water cannon strategy may have prevailed in cooling the damaged nuclear reactors in Fukushima Dai-ichi nuclear plant in Japan. However, the situation remains serious until the reactors had all been stabilised, the United Nations International Atomic Energy Agency said.

Yesterday, Japan authorities initiated dumping of water from a helicopter and from hoses to cool down the nuclear reactors.

According to Tsuyoshi Makigami, chief of nuclear facility management at Tokyo Electric, said at a briefing broadcast by NHK late yesterday: "We were able to see some steam. It's fair to say that the spraying was somewhat effective."

The usual shifting of nuclear power plant staff and volunteers now numbering 300 has kept the reactors from overheating and has continuously pumped water to the exposed rods that may be also be emitting radiation.

The Tokyo Electric Power Company (Tepco) said the shifting of the staff allows for a shorter period of exposure to the dangerous radiation levels.

He noted that the Tokyo Electric engineers have worked overnight to install the 1 kilometre new power line to supply electricity to the nuclear plant. The electricity link is intended to restore power to the plant's cooling systems.

Engineers had finished laying the line to Unit 2 at the plant, the said in a statement on its website. Power will be reconnected to that unit once the spraying of water on Unit 3 ends, the agency said.

The agency said the situation at the three loaded cores -- reactors No. 1, 2 and 3 -- has been "relatively stable" in the last 24 hours.

The threat of radiation in the vicinity and surrounding areas of Tokyo and northeast Japan has prompted foreign governments of the United States and Australia to issue an advisory to their citizens that it is not safe to travel to the said country.