South Korea says it would independently impose new sanctions against 40 individuals and 30 entities for Pyongyang's weapons program and ban any vessels that had stopped at North Korean ports in the past 180 days.
The decision to issue more unilateral sanctions against the North follow a UN Security Council resolution triggered by the isolate state's fourth nuclear test in January and a long-range rocket launch last month.
The sanctioned individuals include a Singaporean and a Taiwanese national.
South Korea would also discontinue participation in a pilot project that brought Russian coal to South Korea through a North Korean port, Rajin, a foreign ministry told reporters in a joint briefing with other government agencies.
The sanctions come as US and South Korean forces conducted annual military exercises amid heightened tensions on the peninsula.