South Korea may announce unilateral sanctions on North Korea after the United Nations Security Council imposes fresh punitive measures over the North's latest long-range missile tests, a government official said Thursday.

The South Korean government is reviewing what unilateral sanctions it can impose on the North after Pyongyang launched two tests of intercontinental ballistic missiles in July.

"Relevant ministries are reviewing them. Last time, the government unveiled unilateral punitive actions after taking into account the UNSC's imposition of sanctions," said an official at Seoul's unification ministry. "I think may have to take into account that factor."

The UNSC has been working on a new tougher sanctions resolution against the North since the North's ICBM test on July 4. But it has made little progress apparently due to opposition from China and Russia.

Seoul imposed two sets of unilateral sanctions against North Korea in response to North Korea's fourth and fifth nuclear tests in 2016. It blacklisted scores of North Koreans and entities suspected of assisting the North's nuclear and missile programs.

President Moon Jae-in on Saturday ordered government officials to consider unilateral sanctions if necessary after the wayward neighbor's ICBM test a day earlier.

But experts said that there is limited room for Seoul to implement effective sanctions amid already strained inter-Korean ties.

Adding more key North Korean figures to the blacklist is largely deemed symbolic as they neither use South Korean financial banks nor have assets here.

US President Donald Trump on Wednesday signed a new sanctions bill on North Korea, Russia and Iran into law.

The sanctions on North Korea targets those supplying the country with crude oil and other products that help its nuclear and missile programs. They also ban goods produced by North Korean forced labor from entering the US. (Yonhap)