Japan said on Friday it would lift entry bans on some cities in Fukushima prefecture that had been designated no-go zones due to their proximity to a nuclear power plant crippled by a powerful earthquake and tsunami last March.

After the natural disasters triggered the worst atomic accident since Chernobyl by causing nuclear fuel meltdowns at the Daiichi power plant in Fukushima, 160 miles (240km) northeast of Tokyo, the government evacuated a 12 mile (20 km) radius of the complex, in which around 80,000 people lived.

"We have decided to revise the restriction bans placed on the evacuation areas," Japanese Prime Minister Yoshihiko Noda said at a nuclear disaster task force meeting.

From April, the government will lift entry bans on Tamura, Minami Soma and Kawauchi, three of the 11 cities and towns that fall within or straddle the 20 km radius.

This follows their declaration in December that the Daiichi plant was in cold shutdown and under control after months of cleanup efforts, signaling it was ready to move to a longer-term phase to eventually decommission the plant.

After lifting the entry bans, the government will separate parts of Tamura, Minami Soma and Kawauchi into three categories, depending on radiation levels.

The government hopes that lifting the entry bans will speed up decontamination by allowing freer access.

In areas where annual radiation measurements are below 20 millisieverts per year, a government safety guideline, residents will have free access to their homes during the day and will be allowed to return permanently at the earliest opportunity post-decontamination.

Where readings are between 20 to 50 millisieverts annually, evacuees will also have unrestricted access during the day although their permanent return will come later.

In areas where measurements top 50 millisieverts, residents will not have free access and they will not be allowed to return for a minimum of five years.

The government is still in talks with the remaining eight cities over lifting the ban.

Even if residents are allowed to eventually return they will continue to live under the shadow of the devastated Daiichi plant, where it's a huge and costly cleanup is expected to take several decades.

Experts at a symposium in San Francisco marking the anniversary of the catastrophe said public radiation exposures have been less than what people were exposed to in the aftermath of the Chernobyl disaster a quarter century ago, according to a report on news website, Environmental Protection.

Speakers at the University of California symposium said monitoring of children living just outside the evacuated zone points to higher than background levels of exposure, but not to unsafe levels, it reported. However, there is uncertainty about harms that may arise due to ingestion of short-lived radioactive iodine in the immediate aftermath of the reactor meltdowns.

Reuters and msnbc.com staff conributed to this report.