Over a dozen Chinese tourists disappeared during a sightseeing tour in the southern city of Busan, with the purpose remaining mysterious, police said Monday.

Busan Metropolitan Police Agency said 13 Chinese visitors -- including seven men -- ran away while traveling to tourist spots in Busan on Sunday. They disembarked from 116,000-ton cruise ship Sapphire Princess in the morning for a day trip in Korea.

“They gradually disappeared in small groups of two or three,” the tour guide was quoted as saying by the police.

While stepping up the stops and searches on foreigners in the city and analyzing the surveillance camera footage, the authorities are probing chances that the missing tourists may be visiting here for crimes, the police said.

“The Chinese tourists taking the Sapphire Princess cruise are usually from high-income groups. It’s unlikely that they disappeared for the purpose of overstaying,” travel agency sources said.

By Lee Hyun-jeong (rene@heraldcorp.com)