RIKUZENTAKATA, Japan (AFP) – Japan's prime minister set foot Saturday in the tsunami zone for the first time since calamity struck three weeks ago, as the UN warned of a "very serious" nuclear situation.

Naoto Kan, who flew into Rikuzentakata on a military helicopter from Tokyo, was also due to stop in nearby Fukushima prefecture, in a show of support for emergency crews risking their lives to prevent meltdown at a nuclear plant.

Rikuzentakata, once known for its picturesque forest and golden beaches, was all but wiped out by the March 11 earthquake and tsunami, and large parts now lie in ruins, with only the shells of a few concrete buildings left standing.

Kan visited an evacuee shelter and then told reporters: "A person who had a house along the coastline asked 'Where could I build a house in the future? I said the government will do its best to support you until the end."

The premier also visited an elementary school which is now home to evacuees such as Michie Sugawara, who welcomed Kan but voiced fears about the future.

"There will be a long road ahead," the 44-year-old woman, whose house was destroyed, told AFP. "This is an unprecedented disaster. I wish he will not forget about us, and I ask for medium and long-term assistance."

The trip was Kan's first ground visit to the disaster zone. He flew over tsunami-hit areas the day after the quake, but a planned visit on March 21 was cancelled, with officials citing poor weather conditions.

In Rikuzentakata, a close-knit community 400 kilometers (250 miles) northeast of Tokyo with a pre-disaster population of nearly 25,000, there are now 1,049 confirmed dead and 1,253 missing as rescue work enters its fourth week.

Along the battered coast, over 11,000 are dead and more than 16,000 missing.

A massive U.S.-Japanese military search for bodies – with 25,000 personnel on helicopters, planes, ships and on the ground – went into its second day, having recovered just 32 bodies on Friday.

The search focused on badly hit Ishinomaki in Miyagi prefecture. Rescuers scoured an elementary school where many children went missing and 50 divers were deployed to the nearby Kitakami River, Kyodo News reported.

Kan was then headed for the "J-village" in Fukushima, the base for hundreds of emergency crew who have been working at great risk to prevent a wider disaster at the tsunami-hit Fukushima Daiichi nuclear plant.

The premier was earlier criticised for flying to the nuclear plant on March 12, the day after the quake, with the conservative opposition alleging that the trip delayed some emergency operations.

The plant has been leaking radiation, triggering worldwide concern, as workers continue tense stop-and-go efforts aimed at shutting it down.   

The environmental impact is worsening, with radioactive materials found in air, soil, groundwater and seawater, even as operator Tokyo Electric Power Company has been criticized for issuing incorrect data at least twice.

With no clear end in sight for efforts to contain the disaster at Fukushima, the head of the UN International Atomic Energy Agency (IAEA), Yukiya Amano, vowed continued help to beleaguered Japan.

"The situation in Fukushima remains very serious", Amano, who is Japanese, said in Nairobi, where he was attending a meeting of the heads of UN agencies.

"But Japan is not alone. The UN secretary general promised me to give all the support necessary to Japan."

In Vienna, the IAEA said that radiation levels recorded at a village outside the evacuation zone around the Fukushima plant were improving daily and now appeared to be back below safe levels.

Earlier in the week, the agency said safe limits had been exceeded at Iitate village, 40 kilometers (25 miles) northwest of Fukushima, well outside the official 20 kilometer exclusion zone.

But by Friday, more samples had been taken and they showed that levels were back below IAEA evacuation criteria.

"The current level is below IAEA recommended limits," said the head of the agency's Incident and Emergency Centre, Elena Buglova.