As many as 10 people died and dozens were injured as Typhoon Halong slammed into the Japanese archipelago over the weekend, reports said Monday, with heavy rain still lashing the country's north.

The storm was moving over the Sea of Japan (East Sea) Monday morning, after making landfall on the largest and most populous island of Honshu at the weekend, the Japan Meteorological Agency said.

The outer bands of the storm were continuing to lash northern Japan with heavy rain as officials warned of landslides, floods and possible tornadoes in the area.

The agency downgraded the typhoon to a tropical storm at 9:00 am (0000 GMT) Monday as it heads toward the far eastern coast of Russia.

The storm, as well as heavy rain last week, killed two people and injured 86 across the country, public broadcaster NHK reported.

But the Nikkei newspaper said as many as 10 deaths were linked to the storm.

Among the victims, the body of an Iranian man was found in Ibaraki, northeast of Tokyo, while two Japanese women died in the country's west, the Nikkei said.

The National Police Agency declined to confirm the number of deaths from the storm, saying it had yet to compile a nationwide total.

The coastguard on Monday resumed searching for a man who went missing apparently while surfing during the storm, off Wakayama in western Japan.

"Police and the coastguard dispatched one rescue boat and two helicopters but we have not found any sign of him," a police spokesman said.

Runaway fireworks

Local officials on Monday scrambled to clean up in the aftermath of the storm.

In Osaka, Halong forced the cancellation of a major fireworks event on Saturday after the storm washed away 21 launching boats, about half of them carrying unused pyrotechnics, a spokesman for the show told AFP.

He declined to elaborate. But NHK reported that the boats, which were later found stuck down river, were carrying thousands of fireworks.

The Osaka city disaster prevention bureau said four workers also drifted away on the runaway boats, but they were later confirmed to be safe.

On Sunday, violent winds destroyed more than 460 buildings in Tochigi prefecture, north of Tokyo, injuring at least two, NHK said.

Weather agency officials were investigating if those winds were actually generated by a tornado.

On Saturday the weather agency had issued its highest warning -- meaning a threat to life and the risk of massive damage -- for Mie prefecture, some 300 kilometres west of Tokyo.

The warning, which was lifted Sunday afternoon, said there could be "unprecedented" torrential rain that might trigger massive landslides and floods.

Local authorities issued evacuation advisories to more than 1.6 million people in total, NHK said.

Airline services largely returned to normal on Monday with just a handful of flights cancelled after more than 700 flights were called off during the weekend, just as Japan began its annual "Obon" summer holiday.

In July, typhoon Neoguri killed several people and left a trail of destruction in southern Japan.