Exactly two years after its north-east coast was wrecked by a deadly tsunami, Japan marked the moment that the most powerful earthquake in its recorded history triggered deadly waves that killed almost 19,000 people, while the prime minister, Shinzo Abe, promised to speed up reconstruction of flattened communities.

In Tokyo and along the tsunami-battered coastline people gathered at memorial services to remember those who died after a magnitude earthquake struck offshore at 2:46pm on 11 March 2011.

Millions across the country stopped work or paused on the street to observe a moment's silence, while the emperor, Abe and relatives of the dead were among 1,200 who attended a ceremony at the capital's national theatre. "I pray that the peaceful lives of those affected can resume as soon as possible," Emperor Akihito said.

Rin Yamane, 18, who lost her mother in the tsunami, said: "Young people from the disaster-hit areas will act so that the disaster will not be a painful memory but a memory that leads to the future."

Almost all of the 26m tonnes of debris left behind by the tsunami has been removed from the three worst-hit prefectures of Iwate, Miyagi and Fukushima, but Monday's remembrance events were tinged with frustration at the slow pace of reconstruction.

In an address, Abe promised to speed up the reconstruction effort, which has been delayed by bureaucratic bungling, labour shortages and a lack of land on higher ground to accommodate residents crammed into tiny temporary shelters.

"Japan will never experience a true spring if spring does not come to north-eastern Japan," he said. "I promise never to forget the weight of each day and to speed up the reconstruction of the region."

Abe, who has made several visits to Fukushima and the tsunami zone since taking office last December, said he planned to increase the budget for rebuilding from 19tn yen (£133bn) to 25tn yen.

"I pledge to achieve reconstruction of the disaster-hit areas and restore the lives of affected people as soon as possible. I will make Japan a country resilient to disasters and stand with the people who were affected," he said.

Two years on, more than 300,000 people are still living in temporary accommodation, and practically no rebuilding has taken place near areas where whole communities once stood, now flattened swaths of land blanketed in grass and weeds.

The earthquake, so powerful it was "heard" by an orbiting satellite 162 miles above Earth, destroyed or damaged 400,000 homes and other buildings. So far, only 10% of permanent homes for displaced survivors have been built.

Among the displaced are 160,000 people from Fukushima prefecture, where radiation levels near the crippled Fukushima Daiichi power plant are still too high for them to return home.

Decontamination work is behind schedule, while some residents have accepted they may never return to neighbourhoods that were irradiated when three reactors went into meltdown, sparking the world's worst nuclear crisis for a quarter of a century.

Tsunami survivors are attempting to put the events of 11 March behind them as they struggle to regain some semblance of normal civic life. "It's scary living here when there is an earthquake … but I don't plan to go anywhere else. I want to give my very best, somehow, towards rebuilding this city," Kenichi Oi, 75, a fisherman in the city of Kesennuma, told Associated Press.

As the country marked the anniversary, the search continued for 2,668 people still missing. More than 2,300 of the recorded deaths have been attributed to the stress of living in evacuation shelters after the disaster or temporary housing.

In Fukushima, frustration is mounting over the lack of progress decontaminating communities at the outer edges of the 12-mile exclusion zone established around the crippled nuclear power plant.

A partial, phased return to some neighbourhoods is under way, but most people who were forced to flee radiation at the height of the crisis have no idea when, or if, their former homes will be fit for human inhabitation.

The mayor of Kawauchi, Yuko Endo, said further delays in work to reduce radiation levels could deter residents from ever returning and put his village's future in doubt. "If I were told to wait for two more years, I might explode," Endo said. "After spending a huge amount of money, with the vegetable patches all cleaned up and ready for farming, we may end up with nobody willing to return."

Expert opinion is inconclusive on the impact long-term exposure to low-level radiation could have on human health. In a recent report, the World Health Organisation said Fukushima residents faced only a tiny increased risk of developing cancer during their lifetimes.

A more immediate threat to health comes from the stress caused by life in small temporary shelters, few job opportunities and the long, complicated process of applying for compensation from the plant's operator, Tokyo Electric Power.

On Monday, 800 evacuees said they were suing the utility, demanding 50,000 yen a month each until radiation levels are brought down to normal levels – a process that authorities conceded could take decades.