As Japan marked the seventh anniversary Sunday of the 2011 earthquake and tsunami that triggered the nuclear disaster, reconstruction efforts have been making progress, but to a varying degree.

Residents in disaster-stricken northeastern Japan have rebuilt their lives and infrastructure has been repaired and redesigned to withstand future disasters.

The March 11 disaster, which left more than 18,000 people dead or missing, also left emotional scars on many in the three hardest-hit prefectures of Iwate, Miyagi and Fukushima. Around 73,000 people have yet to return to their homes towns.

The waves engulfed the Fukushima Daiichi nuclear plant located on the Pacific coast, disabling emergency generators needed to operate pumps to cool its reactors. Three reactors suffered meltdowns, causing hydrogen explosions and the release of radioactive materials.

At 2:46 p.m., when a magnitude 9.0 quake shook the Tohoku region, disaster survivors and people in various parts of the country observed a moment of silence on Sunday. Emperor Akihito and Empress Michiko also offered silent prayers.

"With the passage of seven years, I can see that reconstruction of the affected region is steadily making progress," Prime Minister Shinzo Abe said during a state-sponsored memorial ceremony in Tokyo attended by Prince Akishino and disaster survivors.

But work remains to be done so more people can return to areas affected by the nuclear disaster, Abe said, pledging to speed up reconstruction and provide "seamless" support through different stages of livelihood rehabilitation.

"I would like to make a firm pledge here that the government will exert its united efforts to build a strong and resilient nation that is resistant to disasters."

Some regions have seen their populations and tax revenue returning to pre-disaster levels. But others are still struggling to build houses for people forced to evacuate.

One in 10 people still live in temporary housing in the town of Otsuchi, in Iwate, which lost a third of its town officials in the 2011 calamities.

Some 7,000 households are still living in prefabricated provisional housing in Iwate, Miyagi and Fukushima.

More than 90 percent of the planned 30,000 public apartment units for evacuating households have been built, with the remainder expected to be completed by the end of March next year.

Uncertainty has already been growing over how the Japanese government will support the Tohoku region when its five-year intensive reconstruction period ends in March 2021.

Psychological care takes more time, with Iwate Gov. Takuya Tasso raising the need for longer-term support.

Hidetoshi Onodera, a survivor who represented Miyagi at Sunday's ceremony, called the disaster "an overwhelming ordeal" in his life.

"Until last year, I felt uncomfortable just looking at the ocean, but this year on New Year's Day I visited Nobiru Beach to watch the sunrise for the first time since the disaster," the 69-year-old said.

"The bright and shining sun and the sound of the waves changed my feelings toward life," he said.

In Fukushima, decontamination and other efforts are under way to enable people who lived near the disaster-stricken nuclear plant to return to their hometowns.

But even though evacuation orders have been lifted in many areas around the nuclear facility, about 50,000 of the affected people now reside outside Fukushima Prefecture because of nuclear concerns and for other reasons.

"The reason why we are here is to fulfill our responsibility to Fukushima so let us reaffirm our determination and commitment to reconstruction," Tomoaki Kobayakawa, president of Tokyo Electric Power Company Holdings Inc., told workers at the Fukushima Daiichi nuclear complex.

Safety concerns about nuclear power generation have remained strong. Four opposition parties have jointly submitted a bill calling for the halt of operations at all nuclear power plants in Japan.

But the "zero nuclear power bill" is unlikely to clear the Diet, given that the Abe administration maintains its pro-nuclear policy and is seeking to restart offline nuclear plants. Currently, three are operating out of the 45 commercial reactors in the country.

Carrying placards that read "No to restart of nuclear power plants" and "Let's protect our children," around 5,000 people gathered around the prime minister's office and the Diet building on the seventh anniversary of the Fukushima crisis, according to organizers.

The protest came as Kansai Electric Power Co. is expected to restart the No. 3 reactor of its Oi power plant in Fukui Prefecture in central Japan as early as Wednesday.