South Korea on Tuesday evacuated the majority of teenage scouts from their campsite ahead of an approaching typhoon, the latest disruption to the World Scout Jamboree which has been marred by illness and criticism of its organisation and facilities.

More than 1,000 buses were being deployed to move the scouts out of the southwest, a region that Typhoon Khanun is expected to hit as early as Wednesday.

There were about 36,000 participants at the campsite, near Buan city, and more than two-thirds have already left, Interior Minister Lee Sang-min told reporters.

Seoul and its surrounding province of Gyeonggi would host almost half the scouts, with the rest fanning out to six other areas, Lee said. Police cars and helicopters will escort the convoys to safety, he added.

South Korean organisers are keen to minimise any further problems at the jamboree, the first global gathering of scouts since the pandemic. Since the event began last week, hundreds of participants have fallen ill due to a heatwave, triggering criticism from the public and parents about a lack of preparation.

The British scout contingent, the event's biggest, also left early, citing poor sanitation and food quality, among other concerns. The U.S. scout group followed.

"This is the first time in more than 100 years of World Scout Jamborees that we have had to face such compounded challenges," Ahmad Alhendawi, Secretary General of the World Organization of the Scout Movement, said in a statement.

At the sprawling campsite, scouts dismantled tents and folded up ground sheets, before carrying their backpacks to board nearby buses.

Typhoon Khanun, which has already wreaked havoc in southern Japan, is moving toward South Korea bringing heavy rain and winds of up to 125 kph (78 mph) as of Tuesday afternoon, according to the weather agency.

Khanun is expected to hit southern regions of South Korea on Wednesday afternoon before tracking up the peninsula, prompting the government to raise its typhoon alert to the highest level and close some roads, mountain trails and beaches.

President Yoon Suk Yeol called for thorough preparations for the typhoon, warning of further damage especially in areas struck by last month's torrential rain. He also ordered the scouts to be evacuated without a glitch.

"We will make every effort to ensure their safety until the end of the event, so that young people from all over the world can return home with good memories," Yoon told an emergency meeting held for the typhoon.

Poland is due to host the next World Scout Jamboree in 2027, but President Andrzej Duda cancelled plans to attend this year's closing ceremony due to the typhoon, an official at the Polish Embassy in Seoul said.

A closing ceremony, to be followed by a K-pop concert, will now be held on Saturday at the Seoul World Cup Stadium, the culture ministry said.

South Korea has successfully hosted several major events including the summer and winter Olympic Games, as well as jointly hosting the soccer World Cup with Japan. The port city of Busan is currently bidding to host the Expo in 2030. (Reporting by Hyunsu Yim, Park Ju-min and Hyonhee Shin in Seoul and Hyun Young Yi in Buan; Editing by Ed Davies and Sonali Paul and Miral Fahmy)