SEOUL: Organisers of the World Scout Jamboree in South Korea, who have been grappling with a debilitating heatwave for days, were on Monday preparing for a typhoon to batter their huge campsite with wind and rain, officials said.

Hundreds of those attending the jamboree of about 40,000 scouts from 155 countries have been laid low by temperatures of 33 Celsius (91.4 Fahrenheit), and some troops have pulled out.

The government and organisers have pledged that safety is top priority, and have laid on water trucks, air-conditioned spaces and medics.

But a new danger is looming with Typhoon Kanun due to reach southern South Korea early on Thursday, with strong winds and rain expected, forecasters said.

"To ensure the safety of the World Jamboree, we are discussing detailed countermeasures for the typhoon situation with relevant agencies including the interior ministry," gender equality minister Kim Hyun-sook told a briefing.

The minister said measures would be announced later.

The World Organization of the Scout Movement said in a statement it was monitoring the weather and would ask for help if heavy rain was likely to hit the campsite in an area of reclaimed land in Buan county in southwestern South Korea.

The Australian contingent became the latest troop to leave the campsite, citing the typhoon risk, Australian broadcaster ABC reported.

The U.S. and British contingents have already left because of the heat, with the Americans due to stay at a U.S. army base and the British at hotels in the capital, Seoul.

Singaporean scouts have also moved into accommodation elsewhere but were taking part in on-site activities, the organisers said.

A K-pop concert due to be held at the campsite on Sunday was postponed to Friday and will be held at sports stadium, some 53 km (33 miles) away.

Organisers have come in for criticism from parents and the public for failing to anticipate the heat.

Kim Kwan-young, governor of North Jeolla province hosting the event, apologised on Sunday for not being prepared.

Various authorities and businesses have stepped in to help, donating water and ice cream, while the Jogye Order of Korean Buddhism has opened up its temples to the scouts. (Reporting by Hyunsu Yim; Additional Reporting by Ju-min Park; Editing by Ed Davies, Robert Birsel)