People across Japan paused for a moment of silence at 2:46 p.m. Sunday to mark the one-year anniversary of a powerful earthquake and resulting tsunami that killed more than 19,000 people.

Japan's quake was the strongest recorded in its history and set off the tsunami that swelled to more than 20 metres in some spots along the northeastern coast, destroying tens of thousands of homes.

The disaster also unleashed the world's worst nuclear crisis in more than 25 years when the country's Fukushima Dai-Ichi power plant was severely damaged in the quake, causing meltdowns in three reactors and triggering a widespread exodus.

About 325,000 people are still in temporary housing.

Acts of remembrance Sunday included prayers, silence and reflection that recalled the terrible day when the 9.0 quake struck.

Prime Minister Yoshihiko Noda told citizens that they have overcome many disasters and difficulties in the past and pledged to rebuild the nation so it will be "reborn as an even better place."

Later, he told a news conference he hoped to see the disaster-hit areas fully rebuilt when "babies born on the day of the disasters turn 10 years old."

A siren sounded in one community, Rikuzentakata, which lost 1,691 residents out of its pre-quake population of 24,246. A Buddhist priest in a purple robe rang a huge bell at a temple overlooking an area where houses once stood.

In the seaside town of Onagawa, people faced the ocean and held hands in silent prayer.

Many services continued into the night, with people lighting candles to mourn victims.

Anti-nuclear activists filled the streets of Tokyo, beating drums and shouting slogans as they marched to the headquarters of the Tokyo Electric Power Co, which operates the Fukushima plant.

Protests also occurred in Taiwan's capital as 2,000 people observed a moment of silence for the victims of the Japan disaster before marching in Taipei to renew calls for a nuclear-free island.

In the U.K., activists gathered at a British nuclear power station and blocked the entrance to mark the anniversary.

The Stop Nuclear Now group said hundreds of demonstrators surrounded the closed Hinkley Point station Saturday, some staying overnight.

There were also demonstrations in France near the cities of Lyon and Avignon Sunday.

Meanwhile, U.S. and Philippine troops will train to learn how to deal with a similar aftermath should a massive earthquake hit Manila.

Filipino military spokesman Col. Arnulfo Marcelo Burgos said Sunday that next month's drills would use a computer-generated simulation to test how troops and disaster-response agencies would deal with a "Japan-like" quake.

Debris along Japan's tsunami-ravaged coast still sits in massive piles, with only six per cent disposed of through incineration.

Many towns are still finalizing reconstruction plans, some of which involve moving residential areas to higher, safer ground.

Bureaucratic delays in coordination between the central government and local officials have also slowed rebuilding efforts.

As can be expected, public opposition to nuclear power in the country has grown.

The tsunami shut down the Fukushima plant's cooling systems causing meltdowns in three reactors, releasing radiation into the air that forced the evacuation of 100,000 people.

The Japanese government pledged to reduce reliance on nuclear power, which supplied about 30 per cent of the nation's energy before the disaster.

Emperor Akihito, 78, who recently underwent heart bypass surgery, voiced concern in a speech at the national memorial ceremony about the difficulty of decontaminating land around the plant.

Workers are using everything from shovels and high-powered water guns to chemicals that absorb radiation, but it is a huge, costly project fraught with uncertainty.

"We shall not let our memory of the disasters fade, pay attention to disaster prevention and continue our effort to make this land an even safer place to live," Akihito said.

With files from The Associated Press