Tokyo: A ship carrying about 100 people was swept away by the huge tsunami that hit Japan on Friday and its fate was unknown, public broadcaster NHK reported, citing Miyagi prefecture police.
The ship was owned by a shipbuilder in Ishinomaki, Miyagi, said Kyodo News.
No further information was immediately available from Japanese media or prefectural police which AFP reached by telephone.
Friday's massive quake struck just under 400 kilometres (250 miles) northeast of Tokyo, creating a 10-metre (33 feet) tsunami wave that hit the Pacific coast of Honshu island near Sendai city.
The monster wave wreaked vast destruction, smashing ships into towns and tearing away entire houses.
Television footage shot from a helicopter showed a large whirlpool offshore created by the tsunami that tossed around ships.
Meanwhiel, millions of people in greater Tokyo were stranded far away from home on Friday evening after Japan's biggest earthquake on record shut down the capital's massive subway system.
Countless workers, who had earlier fled violently swaying office blocks, found themselves stuck far from their families -- and unable to speak to them because the overloaded mobile phone system could not carry most calls.
Sirens wailed through Tokyo, television helicopters buzzed overhead and people rushed to the city's ubiquitous 24-hour convenience stores, quickly emptying shelves of bento boxes, sandwiches and instant noodle cups.
"I have no idea how I'll get home," said an 18-year-old woman waiting outside Ginza subway station. She described how ceramics shattered around her in a department store when the huge quake hit mid-afternoon.
"Telephone lines are not working and the subway has completely stopped. I think Tokyo is very fragile right now," said Shintoku Arita, 35.
The government used loudspeaker alerts and TV broadcasts to urge people to stay near their workplaces rather than risk a long walk home, as highways leading out of the city centre were choked and hotels quickly fully booked.
"Please do not try to force your way home when there is no means of transportation, but stay in your offices and other safe places," said an emergency advisory carried by national public broadcaster NHK.
The quake was the largest ever to hit Japan, the fifth strongest tremor worldwide since 1900 and the seventh strongest in history, according to the US Geological Survey and Japanese seismologists.