South Korea and the United States have imposed more sanctions against North Korea over its illegal cyber activities designed to finance the country's nuclear and missile development.

South Korea's Foreign Ministry announced on Tuesday that it newly blacklisted three organizations and seven individuals.

Two of the organizations are affiliated with North Korea's defense ministry or ruling Workers' Party. The third is an academy for tech and cyber training.

The ministry said the organizations illicitly earned money by sending engineers to Russia, China and Laos to engage in building cryptocurrency trading systems.

South Korea has accused North Korean engineers of earning millions of dollars a year by going abroad under fake identities and working.

The US Treasury Department announced on Tuesday that it sanctioned four North Korean entities and one person for their involvement in cryptocurrency theft.

The entities include a training institution for hackers and an intelligence agency unit.

The department said North Korea "conducts malicious cyber activities" to support "its unlawful weapons of mass destruction and ballistic missile programs."