Japan's Prime Minister Naoto Kan has urged all people residing within the 20-km (13 miles) distance from the quake-hit Fukushima 1 nuclear power plant to immediately leave this zone due to increased radiation levels.

A fire, that broke out at the fourth reactor of the Fukushima 1 NPP resulted in the leak of highly concentrated radiation.

"I sincerely ask all citizens within the 20-km distance from the reactor to leave this zone," he said in a televised address.

He also advised those living more than 20-30 km (13-17 miles) from the NPP to stay in their houses, to shut windows and doors and not to turn on air-conditioners.

Japan's Chief Cabinet Secretary Yukio Edano says there are currently no signs that the spent nuclear fuel at the 4th reactor will catch fire.

"Measures are taken to put off the fire. According to our information, there is currently no threat of spent nuclear fuel catching fire," he said.

The French Embassy in Japan said in a statement on its Website that the radiation leak is likely to reach the country's capital, Tokyo, in 10 hours with the current speed of the wind. The Embassy advised its citizens to remain in their houses and to shut all doors and windows firmly.

Radiation levels in the air around the damaged Fukushima nuclear power plant in Japan have risen after another explosion occurred at the 2nd reactor of quake-hit plant at around 6:10 local time (22:10 GMT Monday).

Reuters reported citing plant's operator Tokyo Electric Power Co. that the radiation levels risen four-fold at the reactor. The agency added that the fresh blast damaged the roof and the steam was seen rising from the nuclear complex.

Fears of a large-scale nuclear disaster remain high in Japan as the country continues relief operations following a devastating earthquake and tsunami that have killed nearly 6,000 people and left thousands missing.

TOKYO, March 15 (RIA Novosti)