TOKYO, June 20 -- Japan is sweltering under an unusually intense heatwave that has left at least four people dead from heatstroke and triggered widespread government warnings, as experts say the scorching weather is unlike anything recorded this early in the year.

The Japan Meteorological Agency (JMA) has issued repeated heat alerts since Tuesday, urging residents to stay indoors, hydrate, and check on elderly neighbours.

The heat has been especially punishing for older citizens - all four recorded fatalities were elderly, including a 96-year-old woman found collapsed in a field in Gunma prefecture.

In some parts of the country, temperatures soared more than 10degC above the seasonal average.

Kofu, northwest of Tokyo, reported 38.2deg...