Four South Korean activists who had been detained in China since March after apparently helping North Korean defectors were set to arrive in Seoul late Friday, a government source said.

The activists, including Kim Young-hwan, 49, were arrested on March 29 by Chinese authorities on charges of endangering state security in the northeastern Chinese city of Dalian.

"I heard that Kim and his colleagues were expelled from China and set to return home tonight," the source said on the condition of anonymity. 

Kim was a key proponent of North Korea's guiding "juche" philosophy of self-reliance, but later renounced his pro-North Korean ideology and became active in projects to raise awareness of the North's dismal human rights record. (Yonhap News)