The official toll of the dead and missing following a devastating earthquake and tsunami that flattened Japan's northeast coast has topped 11, 000, with 3, 676 confirmed dead, says police.

The total number of people unaccounted for in the wake of Friday's twin disasters rose by more than 800 to 7, 558, the national police agency said in its latest update.

The number of injured stood at 1, 990.

On Sunday, the police chief of Miyagi, one of the hardest-hit prefectures, said the number of deaths was expected to exceed 10, 000 in his region alone.

Amid a mass rescue effort there were grim updates indicating severe loss of life along the battered east coast of Honshu island, where the monster waves destroyed or damaged more than 55, 380 homes and other buildings.