Japan’s weather agency has declared its deadly heatwave a natural disaster, as the extreme weather continued to break records in the country.

At least 65 people died in the week leading up to Sunday, the fire and disaster rescue agency said, making it the deadliest heatwave since Japan started collating records of such fatalities in 2008.

More than 22,000 people have been taken to hospital with heatstroke symptoms, again a record, making it “the worst ever for any week during summer”, an agency spokesman told the AFP news agency.

It comes after the mercury rose above 41C for the first time in the country’s history, with 41.1C recorded on Monday in the city of Kumagaya, northwest of Tokyo.

And Tokyo’s metro area recorded a temperature above 40C for the first time since records began, with the city’s governor, Yuriko Koike, telling a news conference it was “like being in a sauna”.

The Japan Meteorological Agency said it expected temperatures of 35C or higher to continue into early August.

“We are observing unprecedented levels of heat in some areas,” spokesman Motoaki Takekawa told BBC News, adding the heatwave was “a threat to life and we recognise it as a natural disaster”.

Tourists in Tokyo’s historic Asakusa district struggled with the heat. Cosett Romero from Mexico told reporters she and her family were getting headaches.

“It’s difficult to us because we don’t have this heat in Mexico,” she said.

Authorities have been warning people to take precautions against the heat, including staying inside, drinking plenty of water and using air conditioning.

But the heatwave is also being used as an opportunity to promote traditional, at times ritualistic, ways of staving off the burning sun.

Ms Koike recommended hanging straw screens and taking part in an event known as uchimizu, or “water ceremony”, which involves spraying water on hot pavements and road surfaces.