Japan is marking the first anniversary of a magnitude-9.0 earthquake and tsunami in the northeastern part of the country, which triggered the world's worst nuclear disaster since the 1986 Chernobyl accident.

More than 19,000 people died or went missing in the March 11 twin natural disasters, which also destroyed more than 370,000 houses.

At 05:46 GMT, the precise moment when the earthquake struck one year ago, a moment of silence was observed across the country.

Speaking at a ceremony in Tokyo, Yoshihiko Noda, Japan prime minister, pledged "to speed up ... the reconstruction of the affected areas " and to strengthen nationwide natural disaster measures. He also thanked the volunteers, both foreign and Japanese, who helped with the reconstruction work.

"Predecessors who led Japan's prosperity said that crisis is sometimes necessary in order to grow. We need to support the people who were affected by the earthquake and reconstruct Japan from this historic disaster. And that is my mission," he said.