Japan's Meteorological Agency has advised residents in rain-stricken parts of Nagasaki Prefecture to take all necessary action to preserve their lives.
The agency issued its highest level emergency warning for extremely heavy rain in some cities and towns in the southwestern prefecture on Saturday morning.
Agency official Yasushi Kajihara said rainfall has reached a level the areas have never experienced.
He said there is a very high probability that mudslides and flooding have already struck the affected areas.
He said the situation requires residents to act immediately to protect themselves.
He added the warning could be extended to other municipalities.
He urged residents to follow evacuation advisories without waiting for official warnings.