Tokyo/Fukushima: Japan will freeze plans to build new atomic facilities and carry out a thorough review of its nuclear energy policy, Prime Minister Naoto Kan said on Monday, as robots engaged at the crippled Fukushima plant measured the new radiation level as "tough" for workers.

"We will not proceed with the plans that have been put forward until now" before the government completes a full examination of the accident and makes sure that nuclear plants in the country are safe, Kan told parliament. He pledged a thorough review of the nuclear energy policy in the wake of crisis.

Before the crisis at the Fukushima plant, triggered by the March 11 devastating earthquake and tsunami, the government had set a target of adding 14 or more nuclear power plants by 2030 as part of its efforts to fight global warming. The twin disasters and the two aftershocks have left nearly 28,000 dead or missing.

Speaking in a Diet committee meeting on Monday, Kan said a comprehensive examination is needed to determine why an accident like the one at the Fukushima Daiichi nuclear power plant could have happened.

Kan said he had previously been in favour of nuclear power generation, believing that multi layered safety measures were in place at power plants. But he said all such preconceived, conventional views should be put aside for a review of the nation's nuclear administration.

Radiation levels inside the quake-hit Nos.1 and 3 reactor buildings at the plant were up to about 57 millisieverts per hour, data obtained by remote-controlled robots said.

Tokyo Electric Power Company used US-made remote-controlled robots at the two reactors to measure radiation levels, temperatures and oxygen densities.

It announced that radiation readings were 10 to 49 millisieverts per hour in the No.1 building, and 28 to 57 millisieverts per hour in the No. 3 building.

The earthquake and tsunami had knocked out the Fukushima plant's emergency power supply equipment, which was needed to cool its reactors and spent fuel storage pools.

Based on the collected data, the company will study what kind of work can be done inside the reactor buildings. Meanwhile, the level of contaminated water in the tunnel of the No. 2 reactor continues to rise, state broadcaster NHK said. TEPCO says contaminated water could be flowing into the tunnel since it plugged water leaks from a concrete pit outside the No. 2 reactor into the sea earlier this month.