Record rains in central Japan's Noto region, still recovering from a major New Year's Day earthquake, killed at least one person on Saturday, prompted evacuation orders for tens of thousands and caused blackouts for more than 6,000 households.

Seven people, including four working on quake reconstruction, were missing, and calls for rescue were swamping the fire department, public broadcaster NHK reported.

Hourly rainfall hit record 121 mm on Saturday morning in Wajima, while neighbouring Suzu received 84.5 mm in an hour, also an all-time high. TV footage showed brown floodwater turning streets into rivers in Wajima, with cars half submerged.

Eiichi Higashi, a Wajima resident taking shelter at an evacuation centre within the city, told NHK that people were rushing to the facility as evening neared. “It’s tough to see people who live in temporary housing after losing their houses to the quake now coming to yet another shelter because of the rain,” Higashi said.

Military personnel have been dispatched to the region to work on a rescue mission along with police officers and fire fighters, Chief Cabinet Secretary Yoshimasa Hayashi told reporters.

"This is heavy rain in the region that suffered massive damage by the Noto peninsula earthquake. There must be many people who are very worried," Hayashi said.

The 7.6 magnitude quake killed more than 300 people in Suzu, Wajima and surrounding areas.