SEOUL - An activist from the Republic of Korea was arrested Thursday for his unauthorized trip to the Democratic People's Republic of Korea to mark the death of its late leader Kim Jong-il.

Ro Su-hui, a member of a civic group advocating unification of the two Koreas, crossed the heavily fortified land border to return home 104 days after he made the illegal visit.

He was immediately hauled away by the authorities for questioning over his pro-DPRK activities banned under ROK's controversial National Security Law.

Pyongyang's state media reported the 68-year-old attended events marking the 100th day anniversary of Kim Jong-il's death and met with Kim Yong-nam, president of the Presidium of the Supreme People's Assembly.