US Ambassador Nikki Haley on Friday said reports that Russia had violated UN sanctions resolutions by issuing new work permits to thousands of North Korean labourers were “credible” and “deeply troubling.”

“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.

The Wall Street Journal reported on Thursday that Russia was letting thousands of North Korean labourers enter the country to earn wages that are a source of hard currency revenue for Pyongyang.

The UN Security Council has barred governments from issuing new work permits for North Korean workers, and decided in December that current contracts would be terminated by 2019.

“Credible reports of Russia violating UN Security Council resolutions on North Korean labourers working abroad are deeply troubling,” said Haley.

Last month, Russia and China put a six-month hold on a US request to halt all deliveries of oil products to North Korea after accusing Pyongyang of having illegally imported fuel beyond a cap set in UN resolutions.

“Until we see the final, fully verified denuclearisation of North Korea there can be no easing of sanctions,” said Haley.

The Wall Street Journal reviewed Russian interior ministry records showing that more than 10,000 new North Korean workers had registered in Russia since the ban last year, and at least 700 new work permits issued this year.

Russian government records also show that some Russian companies hiring North Koreans are joint ventures, which are banned under UN sanctions resolutions.

According to the US State Department, about 100,000 North Koreans have been working abroad in recent years, earning as much as $2 billion a year for the regime of Kim Jong Un.

About 24,000 North Koreans were officially working in Russia at the end of 2017, while China also has hosted several thousand labourers from North Korea.