The situation at the Fukushima Daiichi nuclear plant remains very serious nearly two months after it was damaged in an earthquake, a senior official with the United Nations International Atomic Energy Agency (IAEA) said Thursday, as he outlined the ongoing measures taken by the Japanese authorities in response to the accident.

The plant suffered major damage from the earthquake and tsunami that struck the country on 11 March and has been spewing radioactive contamination into the environment ever since.

"Overall, the situation at the Fukushima Daiichi nuclear power plant remains very serious," Denis Flory, IAEA Deputy Director General and Head of the Department of Nuclear Safety and Security, told a news conference in Vienna.

At the same time, he noted that the estimated percentage of core damage to several units of the plant has been revised. The core damage to Unit 1 was revised from an estimated 70 percent to 55 percent, while it was revised from 30 to 35 percent for Unit 2 and from 25 to 30 percent for Unit 3.

This reflects revisions to assessments from 15 March rather than any recent changes in conditions in the reactor cores, he stated.

Flory outlined a number of measures being carried out by Japanese authorities in recent weeks as part of their response to the accident, including the putting in place of counter-measures against water outflow to the sea and to prevent a minimized spread of the radionuclides in water.

The Government has also announced no-entry, planned evacuation and emergency evacuation zones to be applied to specific areas within the vicinity of the plant.

In addition, radiation monitoring continues for 47 prefectures, with the reported values showing that the deposition of radionuclides was still occurring in certain prefectures.

"But the values for deposition are significantly lower than those detected in the first weeks of the emergency and the number of prefectures affected is diminishing," said Flory.

He noted that restrictions on the distribution and/or consumption of milk, and specific types of vegetables, have been in place in five prefectures since they were first imposed on 21 March.

As of 3 May, the only restrictions remaining are in Fukushima prefecture and for two cities in Ibaraki prefecture.

He added that marine monitoring continues near the discharge areas of the plant by the Tokyo Electric Power Company (TEPCO), which owns the plant, as well as at off-shore stations by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT).