Tokyo: Tens of thousands of people across Japan were advised to evacuate, hundreds of flights were cancelled and train services disrupted on election day on Sunday as a typhoon roared towards the coast, bringing heavy rain and strong winds.

Typhoon Lan, classified as an intense Category 4 storm by the Tropical Storm Risk monitoring site, was south of Japan and moving northeast at 50 kph on Sunday night, speeding up slightly, the Japan Meteorological Agency (JMA) said.

Lan appeared to have weakened slightly from its peak, but it was still a powerful storm that could pound parts of Japan with more than 80 mm of rain an hour, an agency official told reporters.

It is set to make landfall on Japan's main island of Honshu, possibly near Tokyo, early on Monday, at which time it is likely to have weakened to a Category 2 storm.

"The wind and rain will grow stronger as the night goes on, so take measures as needed as early as possible, preferably before it gets dark," the official said.

One man was knocked unconscious after scaffolding collapsed at a building site, NHK said. There were a handful of other injuries caused by falls, all minor.

The agency issued warnings for heavy rain and flooding on the Pacific side of Japan including the Tokyo metropolitan area, even though the typhoon is likely to be downgraded.

More than 70,000 households in various parts of Japan were advised to evacuate, with more than 5,000 ordered to do so, NHK public television said.

"I live alone and at night it's scary, so I came here as early as I could," one elderly woman told NHK at a evacuation centre in western Japan.

Wind gusts of up to 180 kph were possible across central and eastern Japan early on Monday, the JMA said, possibly hampering the morning rush hour even after the rain is expected to have largely dissipated.

Several small landslides had occurred and rivers were rising close to the top of their banks. One part received more than 600 mm of rain in 48 hours, twice the usual amount of rain for the whole month of October.

Prime Minister Shinzo Abe told reporters he had called on the government to take steps to minimise any threats to life.

More than 300 flights were cancelled and rail services were interrupted in southern and western parts of the country.

Toyota Motor Corp said it was cancelling the first shift at all of its assembly plants and that it would decide on a later shift around Monday noon.

Abe's ruling bloc was headed for a big win in the election, exit polls showed, potentially reenergising a push towards his cherished goal of revising the post-war, pacifist constitution.

It was not immediately clear how the storm and warnings to evacuate affected voting.