Rescue workers are in a "race against time" to save people caught in devastating record rains that have killed at least 100 people, Japan's prime minister has said.

The torrential downpours have caused flash flooding and landslides across central and western parts of the country, prompting evacuation orders for more than two million people.

Image: Rescue helicopters have been moving people to safety

"Rescues, saving lives and evacuations are a race against time," Shinzo Abe said, as he met with a government crisis committee set up to respond to the disaster.

"There are still many people whose safety has yet to be confirmed."

At least 44 people were missing, local media reported.


Roads collapse in Japan amid heavy flooding

Image: At least 38 people have reportedly died

Around 54,000 rescue workers, police and military personnel have been mobilised to respond to the disaster, which has left entire villages submerged by flooding.

Video from Okayama showed brown water engulfing residential areas with some people fleeing to rooftops and balconies, trying to catch the attention of hovering rescue helicopters.

National broadcaster NHK said water had risen as high as 4.9m (16ft) in the worst-hit areas where cars were seen left in pools of water.

Image: Kurashiki submerged in the south of Japan

Image: The military has been called in to help with the rescue effort

"My house was simply washed away and completely destroyed," Toshihide Takigawa, a 35-year-old employee at a petrol station in Hiroshima, told the Nikkei daily on Saturday.

"I was in a car and massive floods of water gushed towards me from the front and back and then engulfed the road. I was just able to escape, but I was terrified," 62-year-old Yuzo Hori told the Mainichi Shimbun daily in Hiroshima.

Image: Residents stranded in southern Japan

Though the typhoon began last week, the worst of the rain hit from Thursday, when a construction worker was swept away by floodwaters in western Japan.

The toll has risen steadily since then, and the conditions have made rescue operations difficult, with some desperate citizens taking to Twitter to call for help.

"We've never experienced this kind of rain before," an official at the Japanese Meteorological Agency said.

"This is a situation of extreme danger."

As the rescue operations continued, the country also saw a 6.0-magnitude earthquake just outside Tokyo on Saturday, which left buildings swaying in the capital.

However, no tsunami warning was issued and there were no immediate reports of damage despite the strong tremor.