As daylight spread across Japan - revealing scenes of battered homes and a waterlogged landscape - rescue teams set out in helicopters to scour the hardest hit areas for survivors.
Japanese television showed military helicopters rescuing people from rooftops and balconies. One video showed a school in Sendai where the stranded staff and students had painted "S O S" in giant white letters to draw the attention of rescuers. Another clip, above, showed a military helicopter lifting two people to safety from the rooftop of their home, which was surrounded by water and debris.
