Japan has raised the severity of its nuclear disaster to the highest level, putting it on a par with the world's worst disaster nuclear accident at Chernobyl.
A 9.0-magnitude earthquake triggered a tsunami that devastated much of the north-east on 11 March and crippled the Fukushima Daiichi nuclear power plant.
Engineers are no closer to restoring cooling systems at the plant's six reactors, which is critical to bringing down the temperature of overheated nuclear fuel rods.
The disaster at Chernobyl in Ukraine occurred on 26 April 1986 at reactor No 4 when a power outage surge led to a series of explosions and a plume of radioactive smoke, the BBC reports. It was given the highest disaster rating of 7.
Japan on Tuesday raised the severity rating of its nuclear crisis from 5 to 7 as the Fukushima plant has now emitted radiation for more than a month.
However, a spokesperson for Japan's nuclear safety agency told reporters that radiation leaks at the plant are a tenth of those emitted in the Chernobyl disaster.
The meltdown in Ukraine caused thousands of deaths and emitted 10 million times as much radiation.
Authorities say the decision to raise the level reflects the total, continuing release of radiation at the Fukushima plant, rather than a sudden deterioration, and the country will continue to use nuclear power.
Powerful aftershocks continue to hit parts of Japan.
On Tuesday a 6.3 magnitude tremor rattled Fukushima in northeast Japan, while another 6.3 jolt hit Chiba prefecture near Tokyo.
Buildings swayed and trains were halted in the capital, but no tsunami warning was issued.
On Monday, a 7.1-magnitude tremor near Fukushima killed four people, including a 16-year-old girl trapped in a mudslide, and triggered a tsunami alert.
Meanwhile, tens of thousands of people are still homeless due to the 11 March disaster, with many living in evacuation centres set up in schools and temples.
However, in Kamaishi, one of the worst-affected towns the roads have been cleared of wreckage and insurance assessors have begun visiting homes to assess the damage. The process is expected to take years.