People pray under the sunshade to avoid the heat during a service at the Chogye temple in Seoul, South Korea, Aug 2, 2023. (PHOTO / AP)

SEOUL - South Korea raised the hot weather warning to its highest level for the first time in four years, as parts of the country roasted in temperatures over 38 degrees Celsius, the interior and safety ministry said on Wednesday.

The death toll from this summer's heat wave in South Korea rose to at least 23, Yonhap news agency reported, citing the fire authorities.

Two additional deaths from heatstroke were reported on Tuesday, and the estimated death toll rose to 23, more than three times higher than seven deaths tallied during the same period last year.

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Most of the deceased were elderly farmers working outside in the sweltering heat.

Sprinkler trucks spray water on a road to cool the heat in Seoul, South Korea, Aug 2, 2023. (PHOTO / AP)

The heat wave struck the hardest in the southeastern North Gyeongsang province, of which the heatstroke deaths reached 10.

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The official temperature measured in the city of Yeoju, south of Seoul, hit 38.4 C on Tuesday, the Ministry of the Interior and Safety said.

The highest "serious" warning is issued when the apparent temperature is expected at 35 C or higher in at least 40% of the country's 180 regions for three or more days

South Korea raised the heat warning level in its four-tier system to the highest as of 6 pm on Tuesday, the first time since 2019.

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The highest "serious" warning is issued when the apparent temperature is expected at 35 C or higher in at least 40 percent of the country's 180 regions for three or more days. It can also be issued when the apparent temperature is likely to be 38 C or higher for three or more days in 10 percent of the country.

"This weather gets me really sweaty just by walking around," Cho Ye-jin, a 21-year-old college student said, holding a portable fan in one hand in the tourist district of Myeongdong, Seoul. "You can't bear this weather without a fan."

The government forecasts high temperatures to persist with oppressive humidity for the coming days, with the apparent temperature likely to hover around 35 C in most parts of the country.

Members of the South Korean Confederation of Trade Unions cool themselves next to a cooling fog device during a rally against the government's labor policy in Seoul, South Korea, July 6, 2023. (PHOTO / AP)

President Yoon Suk Yeol on Tuesday urged officials to step up measures to prevent further casualties, especially for people working outdoors, the elderly citizens and those living in makeshift houses without adequate air conditioning systems.

Near Yoon's office on Wednesday, construction workers held a press conference and called for concrete countermeasures.

"Under the current conditions, construction workers' heat deaths are 'expected deaths,'" the Korean Confederation of Trade Unions said in a statement.

The growing frequency and intensity of severe weather is symptomatic of global, human-driven climate change, experts in the field say, with heatwaves in much of the world expected to persist through August.