South Korea and Japan on Friday announced their own fresh, unilateral sanctions on North Korea as their nuclear-armed neighbor warns of retaliation against toughened U.N. sanctions over the nuclear and missile tests it conducted this year.

It's still unclear if and how much the South Korean and Japanese measures will sting North Korea, which has been under multiple rounds of U.N. sanctions for years. Trade and exchange programs between the rivals Koreas also largely remain suspended.

The U.N. Security Council voted Wednesday to tighten North Korea sanctions by placing a cap on coal exports, one of the country's main sources for foreign currency. Pyongyang accused Washington of masterminding the sanction and threatened to take unspecified self-defense measures that it said would aggravate regional animosities.

South Korea said Friday it blacklisted dozens of new high-profile North Korean officials and entities by banning South Koreans from engaging in financial dealing with them. Among the North Korean officials are Choe Ryong Hae and Hwang Pyong So, two of leader Kim Jong Un's closest associates, and the blacklisted entities include those involved in coal exports and the dispatch of laborers abroad, according to a South Korean government statement.

The statement said it'll sanction a China-based company and four of its executives for allegedly assisting financial activities by a North Korean bank sanctioned by the U.N. But the company has no assets in South Korea, according to Seoul officials. Earlier this year, the U.S. Justice Department already unsealed criminal charges against Dandong Hongxiang Industrial Development Co. and the individuals.

South Korea said it will also prohibit Seoul-based foreign nuclear and missile experts from re-entering the country if they visit North Korea and commit activities that threaten South Korea's national interest.

In Tokyo, Japan said it was also renewing its sanctions against North Korea. Chief Cabinet Secretary Yoshihide Suga told reporters about the decision and criticized the missile launches and nuclear tests as "a new threat that must not be allowed."