HANOI (Yonhap) -- A Korean activist has been detained in Vietnam in connection with his work related to North Korean defectors, Seoul officials here said Monday.

The 51-year-old activist, who is only identified by his surname Yoo, was arrested by Vietnamese authorities last Wednesday at a hotel in Ho Chi Minh on suspicion of helping North Korean defectors, according to officials at the South Korean embassy in Hanoi.

Yoo was arrested for allegedly helping arrange a way for some North Korean defectors to enter South Korea, but it was not immediately clear what exactly he was accused of doing, officials said.

The South Korean embassy plans to ask the Vietnamese authorities for permission to interview Yoo on Monday.

Yoo is also believed to have played a role in helping more than 400 North Korean defectors fly to Seoul from Thailand in 2004.

Southeast Asian nations, such as Thailand, Vietnam and Laos, have been a preferred transit route for North Korean defectors, who escape through China with the hope of eventually settling in South Korea, home to more than 23,000 North Korean defectors.