UNITED NATIONS/WASHINGTON (Reuters) - The United States on Friday accused Russia of violating U.N. sanctions on North Korea, citing “credible reports” that Moscow was granting new work permits to North Korean laborers despite Russia’s denial of any such actions.

The Trump administration also imposed targeted U.S sanctions on a Russian bank it said had facilitated a transaction with a person blacklisted by Washington for involvement with North Korea’s nuclear weapons program.

This came on the same day that U.S. Secretary of State Mike Pompeo, less than two months after a landmark U.S.-North Korea summit in Singapore, flew back to the city-state and suggested that continued work on weapons programs by North Korea was inconsistent with its leader’s commitment to denuclearization.

Russia denied a report by the Wall Street Journal that said Moscow was allowing thousands of fresh North Korean laborers into the country and granting them work permits in a potential breach of U.N sanctions.

Over 10,000 new North Korean workers have registered in Russia since September, the newspaper said, citing records from Russia’s interior ministry.

Russia’s action potentially violates U.N. sanctions aimed at pressuring Pyongyang to give up its nuclear weapons, the Journal reported, citing U.S. officials.

It also raises further questions about the extent to which North Korea’s larger neighbors, including its biggest trading partner, China, are willing to keep up enforcement of U.S.-led international sanctions on Pyongyang.

In the summit with U.S. President Donald Trump on June 12, North Korean leader Kim Jong Un, who is seeking relief from tough sanctions, committed in broad terms to work towards denuclearization of the Korean peninsula. But Pyongyang has offered no details on how it might go about this, and many experts doubt it will ever give up its nuclear arsenal.

“Credible reports of Russia violating U.N. Security Council resolutions on North Korean laborers working abroad are deeply troubling,” U.S. Ambassador to the United Nations Nikki Haley said later on Friday.

“Talk is cheap - Russia cannot support sanctions with their words in the Security Council only to violate them with their actions,” Haley said in a statement.

RUSSIAN DENIAL

Alexander Matsegora, Russia’s ambassador to North Korea, denied Moscow had allowed any new workers to enter Russia, saying fresh documents had been issued to laborers already based in Russia who were working on old contracts, Interfax news agency reported.

He said the laborers were allowed to work in Russia until Nov. 29, 2019 as their work contracts had been signed before sanctions came into force, Interfax reported. He said 3,500 new work permits had been issued to workers who had signed contracts in Russia before Nov. 29, 2017, Interfax reported.

Labour Ministry records obtained by the Journal showed that a minimum of 700 new work permits had been issued to North Koreans in Russia this year, the paper said.

“It is estimated that North Korean laborers in Russia send between $150-$300 million annually to Pyongyang,” a U.S. State Department spokesperson said. “Moscow should immediately and fully implement all the U.N. sanctions.”

The labor prohibition is a part of a broader array of sanctions aimed at eliminating an important revenue stream for North Korea. Most of the money North Koreans earn abroad ends up in government coffers as workers toil in grueling conditions, the Journal reported.

A separate report released on Thursday by the non-profit research organization C4ADS said initial restrictions in China and Russia - where around 80 percent of North Korean laborers are believed to work - appear to have loosened.

FILE PHOTO: A guard walks along the platform at the border crossing between Russia and North Korea at the North Korean settlement of Tumangan July 18, 2014. The signage reads, "Russia" and "KNDR (Democratic People's Republic of Korea)". REUTERS/Yuri Maltsev/File Photo

In Friday’s sanctions announcement, the U.S. Treasury Department said Moscow-based Agrosoyuz Commercial Bank had conducted “a significant transaction” for Han Jang Su, the Moscow-based chief representative of Foreign Trade Bank (FTB), North Korea’s primary foreign exchange bank.

The Treasury also added Ri Jong Won, the Moscow-based deputy representative of FTB, to its sanctions list and said both Ri and Han should be expelled from Russia.

A separate report released this week by the Seoul-based Asan Institute for Policy Studies said between 2015 and 2017 the Moscow-based Independent Petroleum Company (IPC) sold far more oil to North Korea than what was officially reported.

Russia’s ambassador to North Korea also denied Moscow was flouting U.N. restrictions on oil supplies to North Korea.

In September last year, Reuters found that at least eight North Korean ships that left Russia with a cargo of fuel had headed for their homeland despite declaring other destinations, a ploy that U.S. officials say is often used to undermine sanctions.