A total of 18 North Korean bankers stationed in China, Russia and Libya with suspected links to the regime's weapons programmes have been blacklisted, a statement posted on the South's government website on Monday showed.
"Those individuals have worked overseas, representing North Korean banks and getting involved in supplying money needed to develop weapons of mass destruction," Seoul's foreign ministry said in a statement.
All 18 have already been sanctioned by the US, and the announcement came a day before Mr Trump - who has accused South Korea's dovish President Moon Jae-In of "appeasement" - was due to arrive in Seoul.
The measures were Seoul's first unilateral sanctions under Mr Moon, who took office in May vowing a peaceful resolution to the nuclear standoff and declared a willingness to visit Pyongyang under "the right circumstances".
The move bars South Korean individuals and entities from transacting with those on the list. It will be largely symbolic given a lack of inter-Korean economic ties, but is likely to draw an angry response from Pyongyang.
It also follows a new round of sanctions adopted by the UN Security Council in September following the North's sixth nuclear test and a flurry of missile launches in recent months.
Last year, South Korea unilaterally closed operations at the jointly-run Kaesong Industrial Complex, saying cash from the zone was being funnelled to the North's weapons programme.
The complex was the last remaining form of North-South economic cooperation. Seoul banned nearly all business with the North in 2010 after accusing Pyongyang of sinking one of its warships.
