The team's arrival came as South Korea's new liberal president, Moon Jae-in, is trying to reach out to North Korea despite the North's push to bolster its nuclear and missile programmes.
The North's sole IOC member, Chang Ung, is travelling with the North Korean taekwondo team and will likely meet South Korean officials over cooperation on next year's Winter Olympics in Pyeongchang, South Korea.
Taekwondo is a Korean traditional martial art but has been the subject of a bitter North-South rivalry.
A 15-member ITF demonstration team, all North Koreans, plans to conduct joint performances with WTF athletes, mostly South Koreans, ahead of the WTF-organized world championships, which is set to open Saturday in the southern South Korean town of Muju.
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The rival athletes are to perform at the opening and closing ceremonies in Muju and also in Seoul and the southern city of Jeonju, according to a WTF statement. In 2014, the WTF and ITF agreed to respect each other and form a joint demonstration team during a meeting in China, with IOC President Thomas Bach present.
A North Korean coach and 20 other ITF officials, mostly North Koreans, also came to South Korea. They've become the first North Koreans to visit South Korea since Moon's May 10 inauguration, according to Seoul's Unification Ministry.
Moon's push to improve frayed ties hasn't reported much progress, with the North test-launching a series of newly built missiles. Moon's government has proposed various ideas to use the Pyeongchang Olympics as a way promote peace on the divided Korean Peninsula.