Millions stuck in Tokyo as quake shuts down subways

Millions of people in greater Tokyo were stranded far away from home today evening after Japan's biggest earthquake on record shut down the capital's massive subway system.

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.

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.

"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.

The government used loudspeaker alerts and television broadcasts to urge people to stay near their workplaces rather than risk long walks home, as highways leading out of the city centre were choked and hotels quickly booked out.

"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.

"Night is falling," the NHK newscaster said as chilly darkness fell across the nation.

"If long-distance commuters try to cross prefecture borders on foot at nigh [...]