SEOUL/TOKYO (Reuters) - South Korea and Japan said on Friday they would impose new unilateral sanctions on North Korea over its nuclear and ballistic missile programs, following a fresh U.N. Security Council resolution imposed on the reclusive country this week.

North Korean leader Kim Jong Un attends an intensive artillery drill of the KPA artillery units on the front in this image released by North Korea's Korean Central News Agency (KCNA) in Pyongyang December 2, 2016. KCNA/ via REUTERS

North Korea has rejected the U.N. resolution, aimed at cutting Pyongyang’s annual export revenue by a quarter after its fifth and largest nuclear test in September, as a conspiracy masterminded by the United States to deny its sovereignty.

Both South Korea and Japan already have comprehensive unilateral sanctions in place against North Korea.

South Korea said in a statement its expanded measures would blacklist senior North Korean officials, including leader Kim Jong Un’s closest aides, Choe Ryong Hae and Hwang Pyong So.

Hwang, at one point considered North Korea’s second-most powerful official outside the ruling Kim family, is already subject to U.S. Treasury sanctions.

South Korea also said it would ban entry from the South by foreign missile and nuclear experts if their visits to North Korea were deemed to be a threat to South Korean national interests.

Japan said on Friday it too would add to its own list of unilateral sanctions, including a ban on all ships that have called at ports in North Korea, Chief Cabinet Secretary Yoshihide Suga told a news conference.

“It is a new phase of threat that North Korea forced, carrying out nuclear tests twice this year and launching more than 20 missiles, and it is enhancing capability. Japan absolutely cannot tolerate these acts of violence,” Suga said.

“Japan will consider further measures depending on moves by North Korea and the international society,” he said.

Tokyo will freeze the assets of more groups and individuals connected to North Korea’s nuclear and missile programs, he said.

The U.S. Ambassador to the United Nations, Samantha Power, told the Security Council on Wednesday the United States was realistic about what the new sanctions on North Korea could achieve.

“No resolution in New York will likely, tomorrow, persuade Pyongyang to cease its relentless pursuit of nuclear weapons. But this resolution imposes unprecedented costs on the DPRK (North Korea) regime for defying this council’s demands,” she said.

In February, Seoul suspended operations at a jointly run factory park just inside North Korea, ending the only significant daily interaction across the heavily fortified inter-Korean border.

In March, Seoul released a list of companies and individuals it said were connected to North Korea’s weapons trade and nuclear and missile programs.

South Korea said its new sanctions would expand the entities on that list to include Dandong Hongxiang Industrial Development Co, a Chinese company sanctioned by the United States in September for using front companies to evade sanctions on North Korea’s banned programs.

In Beijing, Foreign Ministry spokesman Geng Shuang said China was opposed to unilateral sanctions and urged countries to proceed cautiously.

“China always firmly opposes unilateral sanctions on a country outside the framework of U.N. Security Council sanctions, and is even more opposed to any party harming China’s reasonable and lawful interests through unilateral sanctions,” he told a regular news briefing.

The new U.S.-drafted U.N. resolution is intended to slash North Korea’s exports of coal, its biggest export item, by about 60 percent with an annual sales cap of $400.9 million, or 7.5 million metric tonnes, whichever is lower.

It also bans North Korean copper, nickel, silver and zinc exports - and the sale of statues. Pyongyang is famous for building huge, socialist-style statues which it exports mainly to African countries.