Japanese media reported at least 1,000 people are presumed dead from Friday's massive 8.9 earthquake, most drowned by the wall of water that swept across the northeast coast of the island nation.
Thousands of others were stranded on rooftops, surrounded by water left by the tsunami that washed over the low-lying farmland of the hardest-hit areas, sweeping away homes, cars, railroads and businesses.
A dam broke early Saturday local time in Fukushima Prefecture, washing away scores more houses in an area where at least 1,800 homes were destroyed by the quake, Kyodo news service said, quoting a Defense Ministry official.
Japanese Prime Minister Naoto Kan appealed for calm in the wake of his nation's worst earthquake since authorities began keeping records 140 years ago. In a nationally televised address, he said an emergency response team had been deployed and international aid was en route.