RIKUZENTAKATA, Japan — Japanese gathered in Tokyo and along the country’s ravaged northeast coast to observe a moment of silence at 2:46 p.m. Friday, exactly five years after a magnitude-9.0 earthquake struck offshore, triggering a devastating tsunami that killed more than 18,000 people and sent reactors at the Fukushima nuclear plant into meltdown.

Some teared up as they held hands or bowed their heads in prayer as sirens sounded on a chilly afternoon in northern Japan. Japanese Emperor Akihito, Empress Michiko and Prime Minister Shinzo Abe, all in formal wear, led a ceremony in Tokyo attended by officials and survivors.

“Many of the people affected by the disaster are aging, and I worry that some of them may be suffering alone in places where our eyes and attention don’t reach,” Akihito said. “It is important that all the people keep their hearts together so that not a single person still in difficulty is overlooked and they can return to normal life as soon as possible.”