Japan's nuclear crisis worsened on Tuesday with the severity level at the damaged Fukushima Daiichi plant increased to a maximum seven level bringing it at par with the 1986 Chernobyl catastrophe in Russia. Earthquakes continue to rock the country, at least six people were killed in the 6.3 magnitude earthquake that struck Chiba prefecture, 77 kms east of Tokyo on Tuesday morning. An aftershock of 7.1 had rocked the northeast on Monday killing one person and injuring five others. Japan is still struggling to recover from the March 11 Earthquake and Tsunami that devastated the northern parts of the country. The decision to raise the threat level at the Fukushima Daichi nuclear plant was made after radiation of 10,000 terabequerels per hour had been estimated at the plant for several hours. Japan's Nuclear and Industry Safety Agency however said radiation emissions from the plant, were a tenth of that from the Chernobyl accident. The agency said, the severity level was upgraded to seven as the impact of radiation leaks has been widespread from the air, vegetables, tap water and the ocean. An official said, level seven signifies a major accident with wider consequences.