Japan plans to lift an advisory telling people living near the no-go zone around the ravaged Fukushima Daiichi nuclear plant to evacuate, a government spokesman said Tuesday.

The government has advised residents in some areas outside the 20-kilometre (12-mile) ring since April 22 to leave due to fears of high radioactive contamination there following the March 11 quake-tsunami disaster which crippled the plant.

People living in other areas within a 20-30 kilometre radius of the plant have been asked to prepare for evacuation in the event of an emergency such as hydrogen gas explosions at the plant.

The government will lift this advisory on evacuation preparations possibly by early September, Chief Cabinet Secretary Yukio Edano told a news conference.

About 58,500 people have homes in these areas and of them about 28,500 have already left.

Edano also said the government would allow evacuees from areas within three kilometres of the plant to make a short trip to their homes as well as business operators to visit their offices in the areas within this month.

These steps were approved by the government Tuesday as it determined that there had been some improvement in the situation at the plant.

The government's task force on the worst nuclear accident since the 1985 Chernobyl disaster concluded there was a low risk of further hydrogen explosions and that the plant's cooling systems were unlikely to fail, Edano said.

The quake and tsunami knocked had out the cooling systems, causing some reactors to melt down and leak radioactive substances into the environment.