China is reported to be accepting fewer workers from North Korea amid growing concerns over Pyongyang's nuclear capabilities and the UN Security Council working to slap new and tougher sanctions.

A labour agent who brings North Koreans to China and gets them to work in restaurants and factories is cited as saying that the number of people coming over has come down in recent weeks.

"I used to bring at least 40-50 North Korean factory workers and waiters across at least once a month but it's less frequent now," Liu, who did not want to give his full name, told Reuters. "I don't think China wants them to come and work here anymore."

Lu Chao, director of a Chinese government think-tank, too confirmed that the numbers have been dropping of late.

"China has been cutting back the number of workers from North Korea it allows in by tightening checks on potential visiting workers and making the paperwork more difficult," Lu said.

According to an estimate by South Korea's state-run think-tank, as many as 150,000 North Koreans are working in China and Russia. The North reportedly takes money from such overseas workers – as much as $900m annually – through official channels and allegedly uses that money to fund its nuclear ambitions.

While it has been Pyongyang's lifeline in the region, China too has been against Kim Jong-un's nuclear and missile programmes. It has agreed to a US-drafted resolution to impose tougher sanctions on Pyongyang. At the same time, it has been arguing that isolating the North further could seriously affect the livelihood of ordinary citizens.

A September report revealed that at least 40 North Korean overseas workers died since January this year. The deaths were attributed to work-related accidents, illness and suicides because of alleged pressure from North Korea on its nationals to send more money.

The squeeze on Kim's regime seems to be affecting businesses and the overall China-North Korea trade as well.

"We're not exporting banned goods, but the sanctions have hit our North Korean business partners so they aren't spending the way they used to," Wang, from the Chinese city of Dandong, said.

North Korea missile threat
Kim Jong Un's regime is accused of taking money, as much as $900m annually, from its citizens working overseas to fund its nuclear ambitions KCNA via Reuters