A group of Japanese citizens said they would file a lawsuit Monday to prevent the restart of a nuclear power plant, a day after the first anniversary of the country's atomic disaster.

The group of 259 citizens are to file the suit in Osaka District Courtseeking an injunction that would block the reopening of utilityKansai Electric's nuclear power plants Oi Unit 3 and 4 in central Fukui prefecture.

On Sunday, tens of thousands rallied near Japan's crippledFukushima plant demanding an end to nuclear power after the March 11 earthquake and tsunami sparked meltdowns at the stricken plant.

The tsunami swamped cooling systems at the Fukushima site and sent three reactors into meltdown, spewing radiation into the environment.

Kiyoko Shimada, a member of the group organising the lawsuit, told AFP that plans to reopen the Oi reactors were premature.

"These reactors are said to be the first in line for the restart of nuclear power plants in Japan after the accident in Fukushima, but given that there are lots of unanswered questions over theFukushima Daiichi plant, it is too early to restart," she said.

"The Oi plants are near active faults and some experts say the plants' quake resistance is not sufficient."

The Japanese government is reportedly planning to approve the restart of the Oi plants as early as this month.

Since last year's accident, the country's commercial nuclear power plants have been undergoing safety inspections with just two out of 54 reactors currently online.

The world's worst nuclear accident in a quarter century has sparked a heightened fear in Japan over atomic power, with several citizen groups having filed or preparing to file injunctions to block other plant restarts.