Prime Minister Shinzo Abe cancelled the annual public ceremony at the National Theatre, attended by members of the royal family and people from the northeastern region hardest-hit by the 2011 tsunami, earthquake and nuclear accident.

The cancellation was extremely regrettable but "it's time to take every possible measure to prevent the spread of infections in our country," said Abe at a small wreath-laying ceremony at his office in Tokyo.

He offered condolences to those who lost loved ones and renewed his pledge to rebuild the disaster-hit region.

"We should not allow precious lessons from the disaster to fade away," Abe added.

The country fell silent for a minute at 2:46 pm (0546 GMT), the exact time a 9.0-magnitude earthquake struck the seabed off Miyagi prefecture on March 11, 2011.

Under light drizzle in Tokyo's Hibiya Park, mourners gathered to pray silently in front of an altar strewn with cherry blossom -- most wearing protective masks.

Naoya Matsuoka, a 32-year-old staff member at a financial company, said it was important to defy the coronavirus to pay respect to the 18,500 killed or missing.

"We are now facing all different issues (like the virus) and hear lots of noise about holding events, but the disaster is something we must not forget. So I am here," he said.

The government has urged the public to cancel or postpone major gatherings or unnecessary outings in a drive to contain the spread of the coronavirus, which has infected 568 people and been linked to 12 deaths in Japan.

The call has resulted in the shutdown of schools and the cancellation or rescheduling of everything from music concerts to football matches, while graduation ceremonies, fashion shows and a sumo tournament have taken place behind closed doors.

- Decades to decommission -

In 2011, the powerful quake triggered violent shaking followed by a towering tsunami, estimated at as high as 17 metres (56 feet) in some areas.

The wave swept Japan's vast northeastern shoreline, killing nearly 16,000 people with more than 2,500 still missing, and overwhelming the emergency power supplies that cooled reactors at the Fukushima Daiichi nuclear plant.

The disaster sent the reactors into meltdown, producing the world's worst nuclear accident since Chernobyl.

The enormous steel-and-concrete buildings that housed the reactors exploded after hydrogen became trapped inside, spreading radioactive material across the region, though no deaths were attributed to the accident directly.

The accident prompted 160,000 to evacuate, many of whom have never returned.

Since then, the government and the plant's operator Tokyo Electric (TEPCO) have managed to bring the reactors to relative stability by pumping water inside to cool them.

But that has led to the accumulation of contaminated water, creating another problem to be solved, potentially by releasing it -- after filtration -- into the sea.

The final decommissioning of the crippled plant is expected to take four decades, but Abe's government hopes to showcase reconstruction so far in the region at this year's Olympics, with the torch relay starting from Fukushima and travelling across affected areas.

The coronavirus outbreak has raised concerns however that the Tokyo Games might be postponed, cancelled or take place behind closed doors. Organisers say preparations are on track, but they have already had to scale back test events and the Olympic flame arrival.

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TEPCO - TOKYO ELECTRIC POWER