More than 30 people are thought to have died and thousands more taken ill as an intense heatwave continues to grip Japan.

Temperatures in excess of 40C have hit central areas of the country this week, with authorities warning more scorching weather is on the way.

In Tokyo, the heat prompted more than 3,000 emergency calls on Wednesday, a record for a single day in the city, while 300 people were hospitalised.

A six-year-old boy died from heatstroke on Tuesday in Aichi prefecutre, central Japan, after he had taken part in a field study with his school at a park.

“We deserve criticism that our judgment [to take students to the park during the heatwave] was wrong,” Takashi Yabushita, principal of Umetsubo Elementary School where the incident happened told Mainichi Shimbun.

“We paid careful attention to prevent students from suffering heatstroke, urging them to drink water.”

Sweltering temperatures are also hindering relief efforts in western Japan, where deadly flooding last week killed more than 200 people.

The heatwave has raised concerns over the welfare of rescue workers and the 4,700 people evacuated from danger areas.

“We are operating in tough conditions, with a severe heatwave in this region,” Koji Kunitomi, a spokesman at the disaster management department in flood-hit Okayama prefecture, told AFP.

Soaring temperatures have also made some question the wisdom of staging the 2020 Tokyo Olympics during July and August, when temperatures often exceed 35C.

Experts have warned the risk of heatstroke in Tokyo has escalated in recent years, saying the Olympics are expected to take place in conditions when sports activities should normally be halted.

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During a visit to Tokyo last week, John Coates, the head of an International Olympic Committee (IOC) inspection team, acknowledged the heat will be a huge challenge for organisers.

"We are mindful that we do have to prepare for extreme heat," he said at a news conference. "You're not the first country to host the games in extreme heat. It's a natural consequence of being in July and August."

Local and national government bodies are planning to lay pavements that emit less surface heat and plant taller roadside trees, but many worry it will not be enough.

The Japan Meteorological Agency has issued warnings over the extremely high temperatures, which look set to continue for several more days, advising the public to take precautions such as drinking water and using air conditioners.