Japan on Friday raised the alert level at quake-damaged Fukushima Daiichi nuclear plant to five from four on a seven-point scale, the UN nuclear watchdog reported.
International Atomic Energy Agency chief Yukiya Amano said efforts to handle the crisis are a "race against the clock."
The change puts Japan's unfolding nuclear crisis two points below the 1986 Chernobyl disaster on the international danger scale for nuclear accidents.
Japan's Nuclear and Industrial Safety Agency graded troubled reactors 1, 2 and 3 at level five, while reactor 4 was rated at level three, Xinhua news agency reported.
Workers at the plant are still desperately trying to cool the overheating nuclear cores in the reactors in an effort to prevent nuclear fallout.
Fukushima was hit by a number of explosions following a 9.0-magnitude earthquake and tsunami that killed thousands on March 11.
The confirmed death toll now stands at 6,405, while over 10,200 are listed missing.
MOSCOW, March 18 (RIA Novosti)
