Six people were killed and 10 remained unaccounted for Sunday as search efforts continued a day after heavy rain hit Noto, a region in Ishikawa Prefecture already devastated by a powerful earthquake.

Rescue operations and restoration work were also ongoing in the area, as record rainfall caused flooding at nearly two dozen rivers and triggered landslides, cutting off roads and isolating more than 100 communities.

Two of the six fatalities were found near a landslide-hit tunnel in Wajima that suffered significant damage from the Jan. 1 earthquake and was under repair, according to the land ministry. Some workers at the site were rescued.

Elsewhere in the prefecture, two people remained missing after being swept away by swollen rivers and eight others were reported as unaccounted for.

In the 48 hours through Sunday afternoon, Wajima recorded almost 500 millimetres of rainfall and Suzu received nearly 400 mm. Both cities on the Noto Peninsula had been under heavy rain warnings since the previous day.

The amount of rainfall in the two cities reached twice the levels for September in an average year. As the heavy rain abated, the weather agency downgraded its "special warnings" for the cities and the town of Noto to simply "warnings" in the morning.

Yet the Japan Meteorological Agency urged people in Ishikawa and Niigata, another prefecture along the Sea of Japan that experienced over 300 mm rainfall in the 48 hours, to maintain strict vigilance against further disasters resulting from heavy rain until noon on Monday.

As the ground in some areas of the two prefectures has loosened due to the magnitude-7.6 quake that struck on Jan. 1, compounded by the rain, even a small amount of further rain could increase the risk of landslides, the agency warned.