The foreign ministry in Seoul said that adding another 20 North Korean companies and 12 individuals to its blacklist would stem the flow of “illegal funding” going towards Pyongyang’s nuclear and missile programmes, Yonhap reported.
The new measures will go into effect on Monday, the news agency reported.
They come just days after Seoul put 18 North Korean banking officials on a blacklist after its foreign ministry said they had “worked overseas, representing North Korean banks and getting involved in supplying money needed to develop weapons of mass destruction”.
Firms targeted by the new restrictions included Korea Daebong and Yusong shipping companies, Koryo Commercial Bank, Agricultural Development Bank and Cheil Credit Bank.
The individuals targeted by sanctions included a spy and several bankers.
Pyongyang has been hit by repeated rounds of UN sanctions after its missile and nuclear tests this year. Its sixth and most powerful nuclear detonation came on 3 September.
That month China, its sole major ally, ordered all North Korean companies inside its borders to close in the face of intense international pressure.
Also on Monday, the South will begin two days of missile tracking drills alongside the US and Japan.
The coming exercises will be the sixth drills sharing information in tracking ballistic missiles among the three nations, Japan’s military said.
It did not say whether the controversial Terminal High Altitude Area Defense system would be involved. The installation of the US’ THAAD system in South Korea has angered China, which fears its powerful radar could look deep into the country and threaten its own security.