SEOUL, South Korea — The world scouting body urged South Korea to cut short the World Scout Jamboree as thousands of British scouts began leaving the coastal campsite Saturday because of a punishing heat wave. American scouts were preparing to pull out, too.

Hundreds of participants have been treated for heat-related ailments since the Jamboree began Wednesday at the site in the coastal town of Buan as South Korea grapples with one of its hottest summers in years.

The World Organization of the Scout Movement said it asked South Korean organizers to "consider alternative options to end the event earlier than scheduled and support the participants until they depart for their home countries."

Should organizers decide to proceed, there needs to be stronger assurances "they will do everything possible to address the issues caused by the heat wave by adding additional resources," the body said in a statement.

"We continue to call on the host and the Korean government to honor their commitments to mobilize additional financial and human resources, and to make the health and safety of the participants their top priority," it said.

The statement came after the U.K. Scout Association announced it was pulling out more than 4,000 British Scouts from the Jamboree and moving them into hotels over the weekend.

The departure of the Jamboree's largest national contingent represented a huge public relations setback for the South Korean hosts, who scrambled to continue the event.

Hundreds of American scouts were also expected to depart the site on Sunday and relocate to a U.S. military base near the South Korean capital, Seoul, said an email the contingent sent to members. It said leaving was necessary because of the "extreme weather and resulting conditions."

The U.S. Embassy in Seoul did not immediately respond to questions on whether the plan to accommodate the scouts at Camp Humphreys had been finalized. But the South Korean organizing committee confirmed that the Americans were among three national contingents that decided to leave as of Saturday afternoon, a group that also included dozens of Singaporean scouts.

Organizers have canceled activities requiring hard physical effort and added more emergency vehicles, medical staff and air conditioning to the site, while Seoul's Foreign Ministry is operating a special taskforce to address concerns raised by foreign diplomatic offices over the safety of the event.

South Korean President Yoon Suk Yeol promised an "unlimited supply" of air-conditioned buses and refrigerator trucks to provide chilled water to the site.

South Korea this week raised its hot weather warning to the highest level for the first time in four years, and temperatures around the country hovered between 35 and 38 degrees Celsius (95 and 100 degrees Fahrenheit) on Friday. According to South Korea's Ministry of the Interior and Safety, at least 19 people have died from heat-related illnesses across the country since May 20.

About 40,000 scouts, mostly teenagers, from 158 countries came to the Jamboree at a campsite built on land reclaimed from the sea. About 4,500 were from the U.K.

Long before the start of the event, critics raised concerns about bringing that many young people to a vast, treeless area lacking protection from the summer heat.

According to South Korea's government, 138 Jamboree participants received treatment for heat-related illnesses Thursday alone. At least 108 participants were treated for similar ailments following Wednesday's opening ceremony.

Choi Chang-haeng, secretary-general of the Jamboree's organizing committee, insisted that the event is safe enough to continue. He linked the large number of patients Wednesday to a K-pop performance during the opening ceremony, which he said left many of the teens "exhausted after actively releasing their energy."