Silent prayers are to be offered at 2:46 pm, the moment the quake struck six months ago triggering a tsunami that devastated swathes of Japan's northeastern coastline and sparked a disaster at the Fukushima Daiichi nuclear plant.

But remembrance plans were overshadowed by early embarrassment for Prime Minister Yoshihiko Noda's new government after trade minister Yoshio Hachiro resigned Saturday over comments deemed insensitive to Fukushima evacuees.

Noda has pledged his government will boost post-disaster recovery efforts but the resignation of one of his cabinet ministers will do little to stem an erosion of faith in Japan's leaders following the March disasters.

Noda on Saturday travelled to ravaged Miyagi and Iwate prefectures for the first time since taking office nine days ago, when he replaced Naoto Kan who resigned amid criticism over his handling of the crisis.

The government has been criticised for its response to the disaster, amid suspicions it underplayed the full scale of the nuclear crisis, and as political infighting overshadowed recovery efforts.

The raging wall of water unleashed by the record 9.0 magnitude quake left an indelible scar along Japan's northeastern coast, leaving 20,000 dead or missing and triggering the worst nuclear crisis since Chernobyl in 1986.

Rebuilding the muddy wastelands of the northeastern "Tohoku" region is expected to cost hundreds of billions of dollars and take up to a decade. Areas close to the Fukushima Daiichi nuclear plant may be uninhabitable for longer.

Radiation fears are a daily fact of life after cases of contaminated water, beef, vegetables, tea and seafood due to the Fukushima accident. The government has been at pains to stress the lack of an "immediate" health risk.

The towering wall of water battered cooling systems at the Fukushima plant, 220 kilometres (138 miles) northeast of Tokyo, leading to reactor meltdowns and the spewing of radiation, forcing tens of thousands to evacuate.

A day ahead of the anniversary, survivors in Soma in Fukushima prefecture held a memorial ceremony for the 459 people dead or missing from the city.

"I promise to address the reconstruction with all my strength and all my heart," said Fukushima governor Yuhei Sato as he stood in front of a stage full of white chrysanthemums.

Hundreds of paper lanterns were released into the sky there at dusk on Saturday, symbolising the souls of those lost in the disaster.

Noda travelled to ravaged Miyagi and Iwate prefectures for the first time since taking office a week ago, when he replaced Naoto Kan who stepped down amid criticism over his handling of the aftermath of the disaster.

But in an early embarrassment for the young government, the newly appointed economy, trade and industry minister was forced to resign Saturday over comments about the crisis-hit Fukushima nuclear plant.

Yoshio Hachiro provoked anger when he called the area around the atomic plant a "shi no machi" or a "town of death".

He denied media reports that after his visit to the plant he also made as if he was rubbing his jacket against a journalist, while making a remark to the effect that "I will infect you with radiation".

But he also declined to elaborate on what exactly happened, saying it was during an unofficial meeting with reporters.

Noda has pledged his government will boost post-disaster recovery efforts but the early resignation of one of his cabinet ministers will do little to stem an erosion of faith in Japan's leaders following the March disasters.

On Saturday the new premier inspected the port city of Kesennuma, one of the most severely damaged communities on the Pacific coast.

Accompanied by the state minister in charge of post-disaster reconstruction Tatsuo Hirano, Noda also visited Iwate prefecture's devastated Rikuzentakata city.

"I saw how massive the tsunami force was with my own eyes," he said, according to Jiji Press. "I would like to see proposals from local residents so that we can help them rise again from this."

After inspecting the destroyed facilities of the Kesennuma fish market, Noda promised local officials that the government will "reflect your needs and opinions on such measures as special economic zones for reconstruction, subsidies and the third extra budget".

Ceremonies to mourn the dead and rallies against nuclear power are scheduled to take place across the nation, with silent prayers to be offered at 2:46 pm on Sunday, the exact moment the quake struck six months ago.

A day ahead of the anniversary, survivors in Soma in Fukushima prefecture held a memorial ceremony for the 459 people dead or missing from the city.

"I promise to address the reconstruction with all my strength and all my heart," said Fukushima governor Yuhei Sato as he stood in front of a stage full of white chrysanthemums.

Hundreds of paper lanterns were released into the sky there at dusk on Saturday, symbolising the souls of those lost in the disaster.

The event was organised by fashion designer Kansai Yamamoto, who held similar memorials in Chernobyl, which experienced a serious nuclear accident 25 years ago, and Indonesia -- the nation hardest hit by the 2004 Asian tsunami.

"These lanterns represent both the souls of the victims and a call for a world that is calm and peaceful," Yamamoto said.

The March 11 tsunami, triggered by a 9.0-magnitude earthquake, ravaged Japan's northeast and left nearly 20,000 dead or missing, according to the latest police figures.

The towering wall of water battered cooling systems at the Fukushima plant, 220 kilometres (138 miles) northeast of Tokyo, triggering the world's worst nuclear accident since Chernobyl.