Tokyo, Mar 15 (PTI): Japan's nuclear crisis veered towards a catastrophe today after explosions at two more reactors and a fire rocked the quake-stricken nuclear power plants at Fukushima and Prime Minister Naoto Kan warned that radiation levels were now high enough to endanger humans.

The blast and fire have turned the nuclear plants 'critical', the country's chief spokesman announced as the melting reactors spewed large amounts of radioactive materials triggering fear of widespread contamination.

Kan in his address to the nation at 11 am local time warned that the radiation had already spread from the crippled reactors and there was 'a very high risk of further leakage' as the French embassy here said that low-level radioactive could reach the capital Tokyo within hours.