Even as a major fire broke out at Reactor Number 4 of the Tsunami crippled Fukushima Daiichi Nuclear Power Station and two fresh earthquakes rocked the country on Tuesday morning, Japan has upgraded its nuclear emergency to a maximum seven on an international scale.

The Fukushima nuclear disaster following the March 11 earthquake and tsunami will now be treated as the highest ranking since Chernobyl disaster in 1986.

Fire fighters and technicians quickly extinguished the fire before it had spread to other areas. Earlier, two earthquakes with a magnitude of 6.3 and 6.4 respectively hit the north eastern areas of the country but no immediate casualties were reported.

The nuclear plant operator, the Tokyo Electric Power Co, told workers trying to stabilize the reactors there to leave the premises immediately. It said the fire was not related to Tuesday's quakes.

Agency reports from Tokyo indicated that the government has decided to order evacuation of people from some more areas surrounding the crippled nuclear plant.