Japan raised the severity of its nuclear disaster to the highest level on Tuesday, putting it on a par with the world's worst disaster nuclear accident at Chernobyl after another major aftershock rattled the quake-ravaged East.

South Korea’s Central Bank froze its key interest rate on Tuesday as it assessed potential global economic threats, including the impact of Japan's devastating earthquake and tsunami.

Chinese telecom equipment supplier ZTE said on Tuesday it was suing a unit of Swedish mobile network giant Ericsson for patent infringement, escalating a legal dispute between the two rivals.

A magnitude 7.1 earthquake jolted the Eastern and Northeastern regions of Japan on Monday, immediately after which a tsunami alert was issued, the Japan Meteorological Agency said.

A tsunami warning was issued for Eastern Japan after a powerful quake hit the country with an epicentre close to the nuclear plant crippled by a huge tsunami a month ago.

As Japan is rocked by a powerful 6.6-magnitude earthquake shortly after holding a minute's silence to mark a month since the massive March 11 quake and tsunami which sparked a nuclear emergency, here is a list of the key events since then: